I don't mean to be rude, but you should check the copper block recipe, it does in fact use 9 ingots. The 2x2 copper ingot recipe is unused, which I double checked before reporting to make sure a copper trapdoor crafted the same as iron wouldn't cause conflicts.
if copper doors/trapdoors can't be switched to use ingots, then perhaps the iron ones should use blocks (I personally hate this idea though)
(I'd also like to mention that getting 2 trapdoors from 6 blocks is an absurdly small return, you lose 5 whole blocks and then some)
I don't mean to be rude, but you should check the copper block recipe, it does in fact use 9 ingots. The 2x2 copper ingot recipe is unused, which I double checked before reporting to make sure a copper trapdoor crafted the same as iron wouldn't cause conflicts.
if copper doors/trapdoors can't be switched to use ingots, then perhaps the iron ones should use blocks (I personally hate this idea though)
(I'd also like to mention that getting 2 trapdoors from 6 blocks is an absurdly small return, you lose 5 whole blocks and then some)