In Richard's own words...
Thanks for your dihedral data from two successful models. The Thunder King was originally designed as a towline glider, like the Hover King, and did quite well in contests.
I have looked at RC-Groups comments about the adequate dihedral angle. Several people (actually more than several) referred to using EDA (Equivalent Dihedral Angle) for sizing the angle. So I looked EDA up and it is based on a plot of Moment Fraction versus Semi-span Station. The Moment Fraction is a measure relating to the rolling moment of the wing and has values of 0 to 1. Semi-span Station of 0 at the root and 1 at the tip. So I did the math using the graph and using the 16° dihedral angle and found the EDA is about 10°. EUREKA!
The 16° dihedral turns out to be about 3.75 inches per foot, which close to Thornburg's number. (Editor's Note: Richard and I consulted Dave Thornburg's Old Buzzard's Soaring Book and reviewed his dihedral rules-of-thumb.) Based on my calculation and other people's data including yours, I'm going to slant the tip panels at 16° for the Thunder King.
Attached (are photos of) the wing with both tips spaced up 5 5/16 inches. They are not glued together yet, I just wanted to see what the wing would look like first.