Well, I moved the battery pack as far back as It would go, which is about half way back towards the tail. I still need about 2 oz to balance it. I think it'll just have to be nose heavy, but of course it would be with a full tank anyway . The Buhor spad I built is very tail heavy and I think it flys ok, so maybe the nose heavy will be OK. I can't bring myself to tear open the fuselage to add weight to it where it's most effective, which is in the tail. ( leverage you know). Maybe the OS 40 LA would be the best choice. How good is that engine? The ST GS40 ringed runs great!