Continuing with wingtip fitting, I block-sanded the trailing edges until they were even with the ailerons:
This caused the trailing edges of the wingtips to become awfully thin, and I was worried about them cracking or splitting. I decided to reinforce the trailing edges by pouring in a thin epoxy/flox mixture and standing the wingtips upright while it cured. Here you're looking down at the inside of one wingtip's trailing edge, with a flox bead drying at the bottom – a terrible photo, I admit:
This is how I secured the wingtips while the epoxy was curing. The inboard ends of the trailing edges are dammed with clear tape, and the bottoms are leveled, all in an effort to get an even application without making a mess:
Here's the finished result after more sanding. This turned out pretty well, and seems to have added plenty of extra strength to the questionable-looking trailing edges:
Next I trimmed the inboard edges to achieve a uniform 1/4" gap between wingtips and ailerons, and cut back the remaining flanges as required for clearance:
