The incidence for the bottom wing is determined by the fuse cutout. I think I set my top wing to exactly the incidence of the bottom wing, or maybe 1 degree neg. (I.E. angled a little down at the leading edge.

It is a trick to get the wings parallel in two planes and at a constant and correct incidence at the same time. My Robart incidence meter was invaluable. Two of them would have been better.

Somehow I seem to remember that a tiny bit of neg incidence in the top wing is desireable in a biplane.

I have a 30 sized Tiger Moth that I could not get the incidence set correctly, and sure enough, it flies a little squirrly.

The Sopwith flies anything but squirrly.