Kevin,

It depends on the bipe. Both a Sig Smith miniplane and a Bel Air bipe balance at the leading edge of the bottom wing. Both of these bipes have a stagger wing set. Meaning the top wing is set futher foward than the bottom wing. Do you have a picture of the airplane?

If it has a staggered wing I would start at 1/4 inch before the leading edge of the bottom wing. Make sure you have plenty of available elevator travel. If it is balanced too far forward you might run out of elevator when trying to land.

Jim