I've got ctenopomas, rope fish, and a synodontis ocellifer with my upper jaws currently. Haven't had any problems although the large male cteno (5.5 inches) can be aggressive to the polys. Used to have an african brown knife which didn't work out; the senegal attacked it repeatedly so I had to rehome it. Also tried Congo tetras hoping they would be fast enough to survive in a heavily planted tank until they were full sized. They didn't last 2 weeks.
I definitely wouldn't try plecos with bichirs again. If they ever get the taste for slime coat they'll end up harassing, and in some instances, killing the bichirs to eat their slime coats.