Fun to play with. But tell me why, when I encode the 26 character alphabet using default settings and no plugboard, upon deciphering it back with a plugboard set to AB, do I get the alphabet back with the AB reversed (as expected) but also with the L transposed by a P, but all the other letters correct? Why should the L change? If additional pairs are added (like CD EF, etc), additional substitutions are made near the middle of the alphabet. Shouldn't only the plugboard pairs change?