RE: sig hog bipe CG problems
Biplanes are often balanced using the top wing. The most recent ones I've done have all had instructions that reference the top wing.
That often gives the commercial balancers fits, btw.
Remember that the CG you're trying to locate is somewhere in the fuselage on most bipes. And whatever device or rig you use to indicate the CG will actually not be holding the wing/airplane "on the CG". The CG will be hanging directly below the line the balancing device has found for you. For example: when "the manual says 3 1/4 from the top wing leading edge" and your balancer winds up holding the top wing 3 1/4" back from the LE and the airplane is teetering there perfectly horizontal with the floor, the CG is somewhere below that line on the top wing.