I noticed today that when you make a set of custom armor, and make it mithral, the Armor Check Penalty is too low. For example, mithral full plate should have an ACP of -3; if you take the pre-made mithral full plate of speed, its ACP is the correct -3. But if you make custom mithral full plate, it shows as -2. Mithral chainmail is the same; it should be ACP -2 -- elven chain is correct, but a custom made mithral chain shows as -1.
I suspect it's applying both the 3 pt reduction for mithral and the 1 pt reduction for being masterwork, but I'm not sure.
I suspect it's applying both the 3 pt reduction for mithral and the 1 pt reduction for being masterwork, but I'm not sure.