Today I made some significant progress. I sanded the aileron and flap ends, where they meet in the middle. Then when I got just enough clearance, I set the wing tip, and floxed the two halves together where I split them earlier. The 8 bid I laid to lengthen the tip works great, and needs only a bit of extra flox to make the thickness at the trailing edge match the aileron.
Wing with all the bits attached
Wing tip re-assembled with longer trailing edge, curing
Flap, aileron, tip trailing edges aligned and matched