I used a pair of 900s in one that I built, it just about took off when on 12v, so I kept dropping a cell(1.2v) and ended up on 7.2v before I sold it. The one which I have just finished is on two Graupner 600s, on two cell Li- Pos and it is adequate, in fact it looks nice on the water, a multi racer it is not. nemesis