Here it is with about a almond sized blob of Bondo spread over the low spots, sloppy seams, inside corners...
The hatch I wanted to be "springy" so that it would form tight to the arched radio compartment opening.
It has a bottom 1/16" thick sheet of basswood that runs lengthwise to the opening and cross grain balsa filler glued on top.
Next are the fins. I want them to be flutter proof, but not too thick. I don't care if they're a little heavy because these planes need tail weight anyway.
What does a Factory Original Demon use for the dorsal fins..?
In the past I think I've used 1/4" or 3/16" balsa, airfoil shaped,
then covered with 6 oz cloth on both sides followed with lighter cloth for a smoother finish.