I don't think one would do well in any of your current setups though. Mine is really skittish and scared of my Nandus Nandus and Juruense catfish. When he is with a vampire tetra though he calms down a bit.
Mine gets nervous if he doesn't have similar tank mates. Mine likes vampire tetras. I am sure some other SA predatory characin would be fine. And of course, other falcirostris are the best tank mates. Although there will be frequent mass panics.
Between vampire tetras he seemed to like to hang out around my Nandus Nandus as well.
And barracudas to feel more comfortable in planted tanks.