I have the CMP Zero-50 size. The engine is YS-110. Even with this engine, I had to add weight to make it slightly nose heavy. I used the CG that was given in the manual. There are 8 other people at my field with the same airplane and engine. Every owner complained that it builds tail heavy with YS-110 in the front. All have used the same CG recommended in the manual. No problems with the airplane flying at 130MPH. The paint is terrible. I used my own hardware. Firewall was reinforced with fiberglass cloth and epoxy.