To find a starting place for CG on a biplane (straight non-tapered wing like the Pup), do the following:

Level the plane on it's main wheels and block it up (wings attached)

Using a large carpenter's square, mark the position of the front of the top wing on the work surface

Take the square and mark the position of the trailing edge of the bottom wing on the work surface.

Measure the distance between these 2 points.

Multiply this dimension by 25% and 30%.

These new numbers are the CG range.

On the underside of the top wing, measure back from the leading edge and mark each side at these dimensions.

This is the starting CG range. Use findertips, CG Machine, whatever, to check balance.

The range may be near the training edge of the top wing.