ive kept rams with a severum before with no problem in the past. severums are pretty peaceful fish, the ones i have had havent been very aggressive at all
It was just a thought, but I've seen some sevs with mouths plenty big enough to inflict some pretty signifigant damage to a ram even if it can't totally inhale it.
I have kept 1" tetras with my old 11" Sev and it didnt touch the ones it grew up with...but any time i added more -gulp-
My Red Spotted Sev is only 2.5" at the mo so may add some Rams of similar size and hope it works out long term...they are not to expensive so not a big risk.
I've found that my severums ignore my other fish, even little guys like Laetacara, juvie keyholes, and juvie Geophagus. The sevs tend to just harass each other. I'm not sure what a lone sev will do.