When I had the Magnum 1.20 4stroke mounted on mine, the balance was perfect with all the radio gear (RX, batt, servos, etc.) in the "radio compartment", without much of an effort. I bought the engine new for less than $200.

Overpower or not, I don't like lead in my planes.

Dennis, I did tell you 1.20 was WAYYY too much for your Hobbistar 60, didn't I? My advice: take that nice 1.20 2stroke out of the Hobbistar and put it on the Spacewalker. Then go buy a .75-.90 for the Hobbistar. That way, you'll end up with both planes moderately overpowered with no lead necessary.

Whatever you choose to do, though, experimenting is half the fun - even if it is somewhat insane. Go for it!