HI:
A friend used a larger carg on the mvvs and they improve a lot ( 15 - 20% even in the 35 cc they enlarged the slot in the longshaft to the widenining it to the size of the inlet at the carb, and it was flipping really good a 20-9 prop.

Also I saw a mvvs providing unlimited vertical to a 72" extra.

I used a ryobi 31 cc, that ios no a big power plant at all in a Golberg Sukhoi and it has almost unlimited performance, but you have to keep your model light.

For the DA 50 I will go to the 27% CAmodel extra 300s, it is a real jewel, light, solid in the corners and no bad habits at all, very good model.
www.camodel.com.ar, I don´t know who is selling it here in the US.

tato.