Admittedly, I don't have a lot of experience with the SKS platform, but the few that I have shot are testaments to the Russians' ability to build a weapon that the user couldn't break with nine-pound hammer. The only times I've seen an SKS misfire it was, like you said, an ammo issue (one instance of cheap rounds, and one instance of a dented cartridge case).
I actually had no idea that they made a bullpup kit for the SKS. The idea has merit, now that I think about it. Lemme know how it turns out once you get it.