I have 10 leatherwing bat skins, but all of the tanner workshop jobs are red.
I can independently confirm this behaviour. I have multiple shorn Drake skins and the Tanner Workshop next door is unable to process them.
Other things I have noted. In the raws of creature_standard.txt
The following duplications exist. I imagine having the exact code twice serves no purpose, but I haven't really played around with modding DF much.
line 1111 YESCASTE[SKILL_RATE:WOODCRAFT:200:0:0:0] is a duplucate of line 1109
line 1112 YESCASTE[SKILL_RATE:WOODCUTTING:200:0:0:0] is a duplucate of line 1110
line 1131 YESCASTE[SKILL_RATE:WOODCRAFT:200:0:0:0] is a duplucate of line 1129
line 1132 YESCASTE[SKILL_RATE:WOODCUTTING:200:0:0:0] is a duplucate of line 1130
Also the reaction in reaction_masterwork.txt
[REACTION:CONCRETE_SLAG_ASH]
[NAME:Make concrete from slag and ash(
]
[BUILDING:SLAG_PIT:CUSTOM_A]
[REAGENT:A:2:NONE:NONE:NONE:NONE][REACTION_CLASS:SLAG] [DOES_NOT_DETERMINE_PRODUCT_AMOUNT]
[REAGENT:B:1:BAR:NONE:ASH:NONE]
[PRODUCT:100:8:BLOCKS:NONE:INORGANIC:CONCRETE]
[SKILL:SMELT]
Seems to produce vastly more then 8 concrete blocks and gives an insane amount of skill increase to SMELTING. As far as I can figure, the only possible cause might be the lack of [DOES_NOT_DETERMINE_PRODUCT_AMOUNT] on reagent B.
Other then that, kudos on the great mod.