Five months on, I've made a little more flap progress. Here are pictures:
1. Slitting the tubes for nylon hinges. This is a Dremel Dangerous Disk mounted in a router on a router table. The block, rod, and arrow shaft segment taped to the carbon tube hold the tube orientation so the slits line up.
2. Using a plug cutter to cut balsa dowels for hinge anchors.
3. Cutting the dowels in two with a band saw. A piece of 1 x 2 with a hole the size of the dowel is clamped to the saw table in front of the blade. A ramrod pushes the dowels through the blade.
4. Cramming the split dowels into the torque tube using the other end of the ramrod, which has an old X-Acto blade glued to it to align the splits in the dowels with the slits in the tube.
5. When the split-balsa-dowel hinge anchors are in place in the tube, I use a piece of Teflon to hold the split open while I Hot Stuff them in place.
6. You can see the end anchor. I finish the flap before installing hinges.