RE: Prop for da-50
Any of you guys that are turning from 6900 to the low 7's with the 50cc engines and better props are right where you want to be. After that it's all about down line braking and absolute vertical thrust levels to suit personal preferences.
The MSC 22-8 is a little different beast. It loads down an engine a bit more due to it's blade width and mass. Some engines like them, some don't. My Brison 3.2's love them. OTOH, my Brison 6.4 performs worse, and with lower rpm numbers, using an MSC 26-10 than it does with a Biela 28-10. Just goes to reinforce the position that a little experimentation with props on engines in the same size range can make a big difference in the performance of a given airframe.