ORIGINAL: britbrat
If you take a typical trainer -- like a Hobbico Superstar, with an OS .40 LA, & fly inverted, it can maintain level flight but will barely be able to climb.
My Afla trainer will climb out of inverted flight fairly easy and i haven't made any changes to it yet. I'm goona put a MDS .68 engine, take out the dihedral, and turn it into a tail dragger.