My plans show the main spar and spar doubler with a long splice joint you glue up before building the wing. If I want to change the dihedral, I have to modify this joint. This joint takes advantage of the six degree dihedral and the splice follows that six degree angle.

1. I could just butt join the two wing halves like many other planes and add a dihedral brace.
2. I could make the splice twice as long to accomodate a reduced dihedral.
3. Or, I could modify the joint somehow to work with a lower angle.

I decided I could cut one side just like before with the six degree splice, and then cut the other side with an equal length three degree per side point. They then fit together perfectly at half the angle.

Diagrams below. The first one shows the original six degree cut used on both sides. The second shows one side with that cut superimposed with the other side cut to a point.