You may want to take a look at the animal-men raws, especially for bug-men, and see how they do it.
Just done some reverse-engineering of said insect-men creatures, it appears to be "working".
The outer layer is now chitin, which is correct, however not the custom chitin in question, simply put the current chitin is not even any were near close to as durable as the chitin I have created and it will not identify as "grelkalan chitin" (see here):
[TISSUE_TEMPLATE:GRELKA_CHITIN_TISSUE]
[TISSUE_NAME:grelkalan chitin:NP]
[SCARS]
[TISSUE_MATERIAL:INORGANIC:GRELKA_CHITIN]
[RELATIVE_THICKNESS:4]
[HEALING_RATE:100]
[VASCULAR:1]
[PAIN_RECEPTORS:1]
[CONNECTS]
[CONNECTIVE_TISSUE_ANCHOR]
[STRUCTURAL]
[TISSUE_SHAPE:STRANDS]
[SETTABLE]
[SPLINTABLE]
which in turn, links to this
[INORGANIC:GRELKA_CHITIN]
[USE_MATERIAL_TEMPLATE:METAL_TEMPLATE]
[STATE_NAME_ADJ:ALL_SOLID:grelka chitin]
[STATE_NAME_ADJ:LIQUID:molten grelka chitin]
[STATE_NAME_ADJ:GAS:boiling grelka chitin]
[DISPLAY_COLOR:6:4:0]
[BUILD_COLOR:6:4:0]
[MATERIAL_VALUE:2]
[SPEC_HEAT:385]
[MELTING_POINT:11952]
[BOILING_POINT:14611]
[SOLID_DENSITY:8930]
[LIQUID_DENSITY:8020]
[MOLAR_MASS:63546]
[IMPACT_YIELD:245000]
[IMPACT_FRACTURE:770000]
[IMPACT_STRAIN_AT_YIELD:175]
[COMPRESSIVE_YIELD:245000]
[COMPRESSIVE_FRACTURE:770000]
[COMPRESSIVE_STRAIN_AT_YIELD:175] 140
[TENSILE_YIELD:70000]
[TENSILE_FRACTURE:220000]
[TENSILE_STRAIN_AT_YIELD:58] 120
[TORSION_YIELD:70000]
[TORSION_FRACTURE:220000]
[TORSION_STRAIN_AT_YIELD:145]
[SHEAR_YIELD:70000]
[SHEAR_FRACTURE:220000]
[SHEAR_STRAIN_AT_YIELD:145] 48
[BENDING_YIELD:70000]
[BENDING_FRACTURE:220000]
[BENDING_STRAIN_AT_YIELD:58]
[MAX_EDGE:10000]
I have a feeling that I am doing something really obviously stupid, but this is the first time I have attempted to extensively redesign a creature, so bare with my stupidity at times.
*re-posting the creature RAW just encase*
[CREATURE:grelka]
[DESCRIPTION:A medium-sized creature prone to great ambition.]
[NAME:grelka:grelkas:grelka]
[CASTE_NAME:grelka:grelka:grelka]
[OUTSIDER_CONTROLLABLE]
[CREATURE_TILE:'G'][COLOR:3:0:0]
[CREATURE_SOLDIER_TILE:154]
[INTELLIGENT]
[STRANGE_MOODS]
[TRANCES]
[BENIGN]
[CANOPENDOORS]
[PREFSTRING:stature]
[BODY:HUMANOID_NECK:2EYES:2EARS:NOSE:2LUNGS:HEART:GUTS:ORGANS:HUMANOID_JOINTS:THROAT:NECK:SPINE:BRAIN:SKULL:5FINGERS:5TOES:MOUTH:TONGUE:FACIAL_FEATURES:TEETH:RIBCAGE]
[BODY_DETAIL_PLAN:CHITIN_MATERIALS]
[BODY_DETAIL_PLAN:CHITIN_TISSUES]
[BODY_DETAIL_PLAN:VERTEBRATE_TISSUE_LAYERS:GRELKA_CHITIN_TISSUE:FAT:MUSCLE:BONE:CARTILAGE]
[REMOVE_TISSUE:SKIN]
[REMOVE_MATERIAL:SKIN]
[USE_MATERIAL_TEMPLATE:NAIL:NAIL_TEMPLATE]
[USE_TISSUE_TEMPLATE:NAIL:NAIL_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:FINGER:NAIL:FRONT]
[TISSUE_LAYER:BY_CATEGORY:TOE:NAIL:FRONT]
[SELECT_TISSUE_LAYER:HEART:BY_CATEGORY:HEART]
[TL_MAJOR_ARTERIES]
[BODY_DETAIL_PLAN:STANDARD_HEAD_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_HEAD_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_RIBCAGE_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_RELSIZES]
[USE_MATERIAL_TEMPLATE:SINEW:SINEW_TEMPLATE]
[TENDONS:LOCAL_CREATURE_MAT:SINEW:200]
[LIGAMENTS:LOCAL_CREATURE_MAT:SINEW:200]
[HAS_NERVES]
[USE_MATERIAL_TEMPLATE:BLOOD:BLOOD_TEMPLATE]
[BLOOD:LOCAL_CREATURE_MAT:BLOOD:LIQUID]
[CREATURE_CLASS:GENERAL_POISON]
[GETS_WOUND_INFECTIONS]
[GETS_INFECTIONS_FROM_ROT]
[USE_MATERIAL_TEMPLATE:PUS:PUS_TEMPLATE]
[PUS:LOCAL_CREATURE_MAT:PUS:LIQUID]
[USE_MATERIAL_TEMPLATE:SWEAT:SWEAT_TEMPLATE]
[USE_MATERIAL_TEMPLATE:TEARS:TEARS_TEMPLATE]
[USE_MATERIAL_TEMPLATE:SPIT:SPIT_TEMPLATE]
[SECRETION:LOCAL_CREATURE_MAT:SWEAT:LIQUID:BY_CATEGORY:ALL:SKIN:EXERTION]
[SECRETION:LOCAL_CREATURE_MAT:TEARS:LIQUID:BY_CATEGORY:EYE:ALL:EXTREME_EMOTION]
[CAN_DO_INTERACTION:MATERIAL_EMISSION]
[CDI:ADV_NAME:Spit]
[CDI:USAGE_HINT:NEGATIVE_SOCIAL_RESPONSE]
[CDI:USAGE_HINT:TORMENT]
[CDI:BP_REQUIRED:BY_CATEGORY:MOUTH]
[CDI:MATERIAL:LOCAL_CREATURE_MAT:SPIT:LIQUID_GLOB]
[CDI:VERB:spit:spits:NA]
[CDI:TARGET:C:LINE_OF_SIGHT]
[CDI:TARGET_RANGE:C:15]
[CDI:MAX_TARGET_NUMBER:C:1]
[CDI:WAIT_PERIOD:30]
[BODY_SIZE:0:0:4000]
[BODY_SIZE:1:168:17500]
[BODY_SIZE:12:0:70000]
[BODY_APPEARANCE_MODIFIER:HEIGHT:75:95:98:100:102:105:125]
[APP_MOD_IMPORTANCE:500]
[BODY_APPEARANCE_MODIFIER:BROADNESS:75:95:98:100:102:105:125]
[APP_MOD_IMPORTANCE:500]
[SET_BP_GROUP:BY_CATEGORY:EYE]
[BP_APPEARANCE_MODIFIER:CLOSE_SET:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:DEEP_SET:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:ROUND_VS_NARROW:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:LARGE_IRIS:25:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[APP_MOD_DESC_RANGE:30:60:90:110:150:190]
[SET_BP_GROUP:BY_CATEGORY:NOSE]
[BP_APPEARANCE_MODIFIER:BROADNESS:25:70:90:100:110:130:200]
[APP_MOD_DESC_RANGE:30:60:90:110:150:190]
[BP_APPEARANCE_MODIFIER:LENGTH:25:70:90:100:110:130:200]
[APP_MOD_DESC_RANGE:30:60:90:110:150:190]
[BP_APPEARANCE_MODIFIER:UPTURNED:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:CONVEX:0:70:90:100:110:130:200]
[APP_MOD_NOUN:nose bridge:SINGULAR]
[SET_BP_GROUP:BY_CATEGORY:EAR]
[BP_APPEARANCE_MODIFIER:SPLAYED_OUT:0:70:90:100:110:130:200]
[APP_MOD_NOUN:ears:PLURAL]
[BP_APPEARANCE_MODIFIER:HANGING_LOBES:0:70:90:100:110:130:200]
[APP_MOD_NOUN:ears:PLURAL]
[BP_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[APP_MOD_NOUN:ears:PLURAL]
[APP_MOD_DESC_RANGE:91:94:98:102:106:109]
[BP_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[APP_MOD_NOUN:ears:PLURAL]
[APP_MOD_DESC_RANGE:91:94:98:102:106:109]
[SET_BP_GROUP:BY_CATEGORY:TOOTH]
[BP_APPEARANCE_MODIFIER:GAPS:0:70:90:100:110:130:200]
[APP_MOD_NOUN:teeth:PLURAL]
[BP_APPEARANCE_MODIFIER:LENGTH:100:100:100:100:100:100:100] for vampires
[APP_MOD_IMPORTANCE:1000]
[APP_MOD_NOUN:teeth:PLURAL]
[APP_MOD_DESC_RANGE:30:60:90:110:150:190]
[SET_BP_GROUP:BY_CATEGORY:SKULL]
[BP_APPEARANCE_MODIFIER:HIGH_CHEEKBONES:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:BROAD_CHIN:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:JUTTING_CHIN:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:SQUARE_CHIN:0:70:90:100:110:130:200]
[SET_BP_GROUP:BY_CATEGORY:THROAT]
[BP_APPEARANCE_MODIFIER:DEEP_VOICE:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:RASPY_VOICE:0:70:90:100:110:130:200]
[SET_BP_GROUP:BY_CATEGORY:HEAD]
[BP_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[APP_MOD_DESC_RANGE:91:94:98:102:106:109]
[BP_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[APP_MOD_DESC_RANGE:91:94:98:102:106:109]
[MAXAGE:60:120]
[ATTACK:PUNCH:BODYPART:BY_TYPE:GRASP]
[ATTACK_SKILL:GRASP_STRIKE]
[ATTACK_VERB:punch:punches]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PREPARE_AND_RECOVER:3:3]
[ATTACK_FLAG_WITH]
[ATTACK_PRIORITY:MAIN]
[ATTACK:KICK:BODYPART:BY_TYPE:STANCE]
[ATTACK_SKILL:STANCE_STRIKE]
[ATTACK_VERB:kick:kicks]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PREPARE_AND_RECOVER:4:4]
[ATTACK_FLAG_WITH]
[ATTACK_PRIORITY:SECOND]
[ATTACK_FLAG_BAD_MULTIATTACK]
[ATTACK:SCRATCH:CHILD_TISSUE_LAYER_GROUP:BY_TYPE:GRASP:BY_CATEGORY:FINGER:NAIL]
[ATTACK_SKILL:GRASP_STRIKE]
[ATTACK_VERB:scratch:scratches]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PREPARE_AND_RECOVER:3:3]
[ATTACK_PRIORITY:SECOND]
[ATTACK:BITE:CHILD_BODYPART_GROUP:BY_CATEGORY:HEAD:BY_CATEGORY:TOOTH]
[ATTACK_SKILL:BITE]
[ATTACK_VERB:bite:bites]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PREPARE_AND_RECOVER:3:3]
[ATTACK_PRIORITY:SECOND]
[ATTACK_FLAG_CANLATCH]
[BABY:1]
[CHILD:12]
[EQUIPS]
[DIURNAL]
[SMELL_TRIGGER:90]
[PROFESSION_NAME:CRAFTSMAN:craftsdwarf:craftsdwarves]
[PROFESSION_NAME:FISHERMAN:fisherdwarf:fisherdwarves]
[PROFESSION_NAME:HAMMERMAN:hammerdwarf:hammerdwarves]
[PROFESSION_NAME:SPEARMAN:speardwarf:speardwarves]
[PROFESSION_NAME:CROSSBOWMAN:marksdwarf:marksdwarves]
[PROFESSION_NAME:AXEMAN:axedwarf:axedwarves]
[PROFESSION_NAME:SWORDSMAN:swordsdwarf:swordsdwarves]
[PROFESSION_NAME:MACEMAN:macedwarf:macedwarves]
[PROFESSION_NAME:PIKEMAN:pikedwarf:pikedwarves]
[PROFESSION_NAME:BOWMAN:bowdwarf:bowdwarves]
[PROFESSION_NAME:MASTER_CROSSBOWMAN:Elite Marksdwarf:Elite Marksdwarves]
[PROFESSION_NAME:MASTER_BOWMAN:Elite Bowdwarf:Elite Bowdwarves]
[HOMEOTHERM:10067]
[APPLY_CREATURE_VARIATION:STANDARD_BIPED_GAITS:900:675:450:225:1900:2900] 39 kph
[APPLY_CREATURE_VARIATION:STANDARD_CLIMBING_GAITS:6561:6115:5683:1755:7456:8567] 5 kph, NO DATA
[APPLY_CREATURE_VARIATION:STANDARD_SWIMMING_GAITS:5341:4723:4112:1254:6433:7900] 7 kph
[APPLY_CREATURE_VARIATION:STANDARD_CRAWLING_GAITS:2990:2257:1525:731:4300:6100] 12 kph, NO DATA
[SWIMS_LEARNED]
[MANNERISM_FINGERS:finger:fingers]
[MANNERISM_NOSE:nose]
[MANNERISM_EAR:ear]
[MANNERISM_HEAD:head]
[MANNERISM_EYES:eyes]
[MANNERISM_MOUTH:mouth]
[MANNERISM_HAIR:hair]
[MANNERISM_KNUCKLES:knuckles]
[MANNERISM_LIPS:lips]
[MANNERISM_CHEEK:cheek]
[MANNERISM_NAILS:nails]
[MANNERISM_FEET:feet]
[MANNERISM_ARMS:arms]
[MANNERISM_HANDS:hands]
[MANNERISM_TONGUE:tongue]
[MANNERISM_LEG:leg]
[MANNERISM_LAUGH]
[MANNERISM_SMILE]
[MANNERISM_WALK]
[MANNERISM_SIT]
[MANNERISM_BREATH]
[MANNERISM_POSTURE]
[MANNERISM_STRETCH]
[MANNERISM_EYELIDS]
[SPOUSE_CONVERSION_TARGET]
[MUNDANE]
[CASTE:FEMALE]
[FEMALE]
[MULTIPLE_LITTER_RARE]
[CASTE:MALE]
[MALE]
[SET_BP_GROUP:BY_TYPE:LOWERBODY][BP_ADD_TYPE:GELDABLE]
[SELECT_CASTE:ALL]
[SET_TL_GROUP:BY_CATEGORY:EYE:EYE]
[TL_COLOR_MODIFIER:IRIS_EYE_AMBER:1:IRIS_EYE_AQUA:1:IRIS_EYE_AQUAMARINE:1:IRIS_EYE_ASH_GRAY:1:IRIS_EYE_AUBURN:1:IRIS_EYE_AZURE:1:IRIS_EYE_BLUE:1:IRIS_EYE_BRASS:1:IRIS_EYE_BRONZE:1:IRIS_EYE_BROWN:1:IRIS_EYE_CERULEAN:1:IRIS_EYE_CHESTNUT:1:IRIS_EYE_CHOCOLATE:1:IRIS_EYE_CINNAMON:1:IRIS_EYE_COPPER:1:IRIS_EYE_DARK_BLUE:1:IRIS_EYE_DARK_BROWN:1:IRIS_EYE_DARK_CHESTNUT:1:IRIS_EYE_DARK_GREEN:1:IRIS_EYE_DARK_OLIVE:1:IRIS_EYE_DARK_TAN:1:IRIS_EYE_ECRU:1:IRIS_EYE_EMERALD:1:IRIS_EYE_FERN_GREEN:1:IRIS_EYE_GRAY:1:IRIS_EYE_GREEN:1:IRIS_EYE_JADE:1:IRIS_EYE_LIGHT_BLUE:1:IRIS_EYE_LIGHT_BROWN:1:IRIS_EYE_MAHOGANY:1:IRIS_EYE_MIDNIGHT_BLUE:1:IRIS_EYE_OCHRE:1:IRIS_EYE_OLIVE:1:IRIS_EYE_PALE_BLUE:1:IRIS_EYE_PALE_BROWN:1:IRIS_EYE_PALE_CHESTNUT:1:IRIS_EYE_PERIWINKLE:1:IRIS_EYE_PINE_GREEN:1:IRIS_EYE_RAW_UMBER:1:IRIS_EYE_RUSSET:1:IRIS_EYE_SEA_GREEN:1:IRIS_EYE_SEPIA:1:IRIS_EYE_SKY_BLUE:1:IRIS_EYE_SLATE_GRAY:1:IRIS_EYE_SPRING_GREEN:1:IRIS_EYE_TAN:1:IRIS_EYE_TAUPE_DARK:1:IRIS_EYE_TAUPE_GRAY:1:IRIS_EYE_TAUPE_MEDIUM:1:IRIS_EYE_TAUPE_PALE:1:IRIS_EYE_TAUPE_SANDY:1:IRIS_EYE_TEAL:1:IRIS_EYE_TURQUOISE:1]
[TLCM_NOUN:eyes:PLURAL]
Thanks for your patience.