RE: DA50-Yellow Spit. Prop?
If you're going to have the spinner cut, it might be worth cutting it to fit a 12 pitch prop, in case you ever want to use one. I use a 22x10 on my Yellow Spit with a FPE 3.4 (55cc) and it is pretty fast. For a DA 50, I would think a 21x10 would work well, but perhaps cut the spinner to accept a 20x12, as suggested by Jeff Q.
-Ed B.