G'day again, Yes I did add quite a bit of lead to the engine mount, can't remember how many ounces. Yes a .70 will work, Whats your altitude, I'm at 4500 feet [ can't figure it in meters]. 14-8 master airscrew prop works pretty good. I've only had two flying days in two full months where I live at here in Utah. Snow/ fog/ haze all the time. Let me know how your's turns out. Seeya, MM