Under tissue_template...
[RELATIVE_THICKNESS:1] <- Might try making a new tissue for your creature for it's scales/leather/chitin/whatever and increase this number.
Under material_template_default...
[MATERIAL_TEMPLATE:SKIN_TEMPLATE]
[STATE_COLOR:ALL_SOLID:GRAY]
[STATE_NAME:ALL_SOLID:skin]
[STATE_ADJ:ALL_SOLID:skin]
[STATE_COLOR:LIQUID:GRAY]
[STATE_NAME:LIQUID:n/a]
[STATE_ADJ:LIQUID:n/a]
[STATE_COLOR:GAS:GRAY]
[STATE_NAME:GAS:n/a]
[STATE_ADJ:GAS:n/a]
[DISPLAY_COLOR:7:0:0]
[MATERIAL_VALUE:1]
[SPEC_HEAT:4181]
[IGNITE_POINT:10508]
[MELTING_POINT:NONE]
[BOILING_POINT:NONE]
[HEATDAM_POINT:10250]
[COLDDAM_POINT:9900]
[MAT_FIXED_TEMP:NONE]
[SOLID_DENSITY:1000]
[LIQUID_DENSITY:NONE]
[MOLAR_MASS:NONE]
[IMPACT_YIELD:10000]
[IMPACT_FRACTURE:10000]
[IMPACT_ELASTICITY:50000]
[COMPRESSIVE_YIELD:10000]
[COMPRESSIVE_FRACTURE:10000]
[COMPRESSIVE_ELASTICITY:50000]
[TENSILE_YIELD:10000]
[TENSILE_FRACTURE:10000]
[TENSILE_ELASTICITY:50000]
[TORSION_YIELD:10000]
[TORSION_FRACTURE:10000]
[TORSION_ELASTICITY:50000]
[SHEAR_YIELD:20000] used data for human skin
[SHEAR_FRACTURE:20000]
[SHEAR_ELASTICITY:50000]
[BENDING_YIELD:10000]
[BENDING_FRACTURE:10000]
[BENDING_ELASTICITY:50000]
[MAX_EDGE:0]
[ABSORPTION:100]
This lets the game know to use this item to determine the exact material type for the leather product in the tanning reaction.
[MATERIAL_REACTION_PRODUCT:TAN_MAT:LOCAL_CREATURE_MAT:LEATHER]
This lets the game know that an animal was likely killed in the production of this item.
[IMPLIES_ANIMAL_KILL]
[ROTS]
[MATERIAL_TEMPLATE:SCALE_TEMPLATE]
[STATE_COLOR:ALL_SOLID:GRAY]
[STATE_NAME:ALL_SOLID:scale]
[STATE_ADJ:ALL_SOLID:scale]
[STATE_COLOR:LIQUID:GRAY]
[STATE_NAME:LIQUID:n/a]
[STATE_ADJ:LIQUID:n/a]
[STATE_COLOR:GAS:GRAY]
[STATE_NAME:GAS:n/a]
[STATE_ADJ:GAS:n/a]
[DISPLAY_COLOR:7:0:0]
[MATERIAL_VALUE:1]
[SPEC_HEAT:420]
[IGNITE_POINT:10508]
[MELTING_POINT:NONE]
[BOILING_POINT:NONE]
[HEATDAM_POINT:10250]
[COLDDAM_POINT:9900]
[MAT_FIXED_TEMP:NONE]
[SOLID_DENSITY:500]
[LIQUID_DENSITY:NONE]
[MOLAR_MASS:NONE]
[IMPACT_YIELD:10000]
[IMPACT_FRACTURE:10000]
[IMPACT_ELASTICITY:100000]
[COMPRESSIVE_YIELD:10000]
[COMPRESSIVE_FRACTURE:10000]
[COMPRESSIVE_ELASTICITY:100000]
[TENSILE_YIELD:10000]
[TENSILE_FRACTURE:10000]
[TENSILE_ELASTICITY:100000]
[TORSION_YIELD:10000]
[TORSION_FRACTURE:10000]
[TORSION_ELASTICITY:100000]
[SHEAR_YIELD:60000]
[SHEAR_FRACTURE:120000]
[SHEAR_ELASTICITY:100000]
[BENDING_YIELD:10000]
[BENDING_FRACTURE:10000]
[BENDING_ELASTICITY:100000]
[MAX_EDGE:0]
[ABSORPTION:100]
[IMPLIES_ANIMAL_KILL]
[MATERIAL_TEMPLATE:LEATHER_TEMPLATE]
[STATE_COLOR:ALL_SOLID:BROWN]
[STATE_NAME:ALL_SOLID:leather]
[STATE_ADJ:ALL_SOLID:leather]
[STATE_COLOR:LIQUID:BROWN]
[STATE_NAME:LIQUID:n/a]
[STATE_ADJ:LIQUID:n/a]
[STATE_COLOR:GAS:BROWN]
[STATE_NAME:GAS:n/a]
[STATE_ADJ:GAS:n/a]
[DISPLAY_COLOR:6:0:0]
[MATERIAL_VALUE:1]
[SPEC_HEAT:420]
[IGNITE_POINT:10508]
[MELTING_POINT:NONE]
[BOILING_POINT:NONE]
[HEATDAM_POINT:10250]
[COLDDAM_POINT:9900]
[MAT_FIXED_TEMP:NONE]
[SOLID_DENSITY:500]
[LIQUID_DENSITY:NONE]
[MOLAR_MASS:NONE]
[IMPACT_YIELD:10000]
[IMPACT_FRACTURE:10000]
[IMPACT_ELASTICITY:50000]
[COMPRESSIVE_YIELD:10000]
[COMPRESSIVE_FRACTURE:10000]
[COMPRESSIVE_ELASTICITY:50000]
[TENSILE_YIELD:10000]
[TENSILE_FRACTURE:10000]
[TENSILE_ELASTICITY:50000]
[TORSION_YIELD:10000]
[TORSION_FRACTURE:10000]
[TORSION_ELASTICITY:50000]
[SHEAR_YIELD:25000] -- was 15 to 37 MPa in animal byproducts net pdf
[SHEAR_FRACTURE:25000]
[SHEAR_ELASTICITY:50000]
[BENDING_YIELD:10000]
[BENDING_FRACTURE:10000]
[BENDING_ELASTICITY:50000]
[MAX_EDGE:0]
[ABSORPTION:40]
[IMPLIES_ANIMAL_KILL]
[LEATHER]
[ITEMS_LEATHER]
[MATERIAL_TEMPLATE:SHELL_TEMPLATE]
[STATE_COLOR:ALL_SOLID:DARK_GREEN]
[STATE_NAME:ALL_SOLID:shell]
[STATE_ADJ:ALL_SOLID:shell]
[STATE_COLOR:LIQUID:DARK_GREEN]
[STATE_NAME:LIQUID:n/a]
[STATE_ADJ:LIQUID:n/a]
[STATE_COLOR:GAS:DARK_GREEN]
[STATE_NAME:GAS:n/a]
[STATE_ADJ:GAS:n/a]
[DISPLAY_COLOR:2:0:0]
[MATERIAL_VALUE:1]
[SPEC_HEAT:1000]
[IGNITE_POINT:10508]
[MELTING_POINT:NONE]
[BOILING_POINT:NONE]
[HEATDAM_POINT:10250]
[COLDDAM_POINT:9900]
[MAT_FIXED_TEMP:NONE]
[SOLID_DENSITY:500]
[LIQUID_DENSITY:NONE]
[MOLAR_MASS:NONE]
[IMPACT_YIELD:10000]
[IMPACT_FRACTURE:10000]
[IMPACT_ELASTICITY:100]
[COMPRESSIVE_YIELD:10000]
[COMPRESSIVE_FRACTURE:10000]
[COMPRESSIVE_ELASTICITY:100]
[TENSILE_YIELD:10000]
[TENSILE_FRACTURE:10000]
[TENSILE_ELASTICITY:100]
[TORSION_YIELD:10000]
[TORSION_FRACTURE:10000]
[TORSION_ELASTICITY:100]
[SHEAR_YIELD:115000] used bone, no data
[SHEAR_FRACTURE:130000]
[SHEAR_ELASTICITY:100]
[BENDING_YIELD:10000]
[BENDING_FRACTURE:10000]
[BENDING_ELASTICITY:100]
[MAX_EDGE:1000]
[ABSORPTION:100]
[IMPLIES_ANIMAL_KILL]
[SHELL]
[ITEMS_HARD]
[ITEMS_SCALED]
[MATERIAL_TEMPLATE:CHITIN_TEMPLATE]
[STATE_COLOR:ALL_SOLID:GRAY]
[STATE_NAME:ALL_SOLID:chitin]
[STATE_ADJ:ALL_SOLID:chitin]
[STATE_COLOR:LIQUID:GRAY]
[STATE_NAME:LIQUID:n/a]
[STATE_ADJ:LIQUID:n/a]
[STATE_COLOR:GAS:GRAY]
[STATE_NAME:GAS:n/a]
[STATE_ADJ:GAS:n/a]
[DISPLAY_COLOR:7:0:0]
[MATERIAL_VALUE:1]
[SPEC_HEAT:420]
[IGNITE_POINT:10508]
[MELTING_POINT:NONE]
[BOILING_POINT:NONE]
[HEATDAM_POINT:10250]
[COLDDAM_POINT:9900]
[MAT_FIXED_TEMP:NONE]
[SOLID_DENSITY:500]
[LIQUID_DENSITY:NONE]
[MOLAR_MASS:NONE]
[IMPACT_YIELD:10000]
[IMPACT_FRACTURE:10000]
[IMPACT_ELASTICITY:100]
[COMPRESSIVE_YIELD:10000]
[COMPRESSIVE_FRACTURE:10000]
[COMPRESSIVE_ELASTICITY:100]
[TENSILE_YIELD:10000]
[TENSILE_FRACTURE:10000]
[TENSILE_ELASTICITY:100]
[TORSION_YIELD:10000]
[TORSION_FRACTURE:10000]
[TORSION_ELASTICITY:100]
[SHEAR_YIELD:115000] used bone, no data
[SHEAR_FRACTURE:130000]
[SHEAR_ELASTICITY:100]
[BENDING_YIELD:10000]
[BENDING_FRACTURE:10000]
[BENDING_ELASTICITY:100]
[MAX_EDGE:1000]
[ABSORPTION:100]
[IMPLIES_ANIMAL_KILL]
These are all different "outer" layers, skin, leather, chitin, that sort of stuff.
The YIELD and FRACTURE for IMPACT, COMPRESSIVE, TENSILE, all seem to be the same within each entry. so you'd probably want to leave those as is. The SHEAR entry seems to have a lower yield and than fracture for some. That'd I suppose imply that it's a harder material. BENDING seems to be on the low end of ELASTICITY for hard materials like BONE and CHITIN, implying less movement.
To really understand all these you need to understand what it means by IMPACT, COMPESSIVE, TESNILE, TORSION, SHEAR, BENDING.
Impact I believe is how well it does with well... impacts. A higher number might make it less susceptible to bludgeoning weapons.
Compressive might imply of how well the item can compress, might influence movement and might also influence how ridged and strong the item is to... bludgeoning blows.
Tensile could imply how well it does with being stretched. Like if you use one string, the tensile strength is to that of the one string and is relatively low and if you hang something too heavy on it, it snaps, if you make it into a rope, with many strands it can take the weight and the therefore, the thing is strong. It's like taking cotton and metal wire, the metal wire obviously has a higher tensile strength cause it can hold a much heavier item.
Torsion is how well something can be twisted. If you take glass, and you twist it, it breaks relatively quick, a large piece of glass allows for a little bit more visible twisting, if you take a sheet of aluminum and twist it, it can twist a decent amount for a metal and still retain its original shape, so this could imply mobility.
Shear strength implies possibly how well the item can be cut. A piece of bread has a low shear strength and you cut it relatively easy with a knife, but if you use a dull knife on the bread, it's compression needs to hold up to the pressure you apply before you can cut the bread or else it deforms.
Bending is well... how well it bends. Chitin or a shell would have relatively no bending as it is a really hard material and has to stay firm or it just breaks and is useless, but you lose out on mobility for strength. Metal has a bending ability, take a knife or a sheet of metal again and you can bend it, however you can bend it only so far or its shape is altered and is now bent, with a cold metal, the metal could bend just a bit and then snap.
With the way the game seems to take all of these numbers. Higher numbers mean stronger armor and more mobile armor IMO.
Hope this helps.