Tomd, I think I'll install one on of my old planes and see if it's actually capable of correcting for wind gusts and drifts.
I balanced the BH-2 today. CG is right at 70mm, with no additional lead for balance. The only real concession to balance I made was the use of a Dubro chromed brass spinner nut. I don't know what that spinner nut actually weighs, but it did the trick. So, with the Magnum 52, and a 6 volt (5 cell) battery mounted underneath the fuel tank, a Master Airscrew 11x6 three bladed prop and the Dubro chromed brass spinner...the airplane balances where it should.
Tomorrow, I'll tweak the motor. It's already broken in but needs some low end tweaking. Then just wait for a reasonably light wind day for the maiden flight.