Mine is an SV26, runs like a top, but I had set the timing at 30 degrees BTDC (was 10 deg off), had to add a choke (from weedeater), and when the ears broke, I ground them all off, and added an aluminum plate between the reeds and the case. As you can see by my video, the 26 flys it just fine. Maybe a 30 would be nice, but I don't need any more power. I like my planes to fly like the real one's. A 50 goes nice on a 1/3 scale Pitts though...
http://www.youtube.com/watch?v=rywOLmPgeIc