After retrieving the right aileron from storage and re-reading the instructions to figure out what was next, I started by measuring and cutting a piece of the VA-140 trailing edge extrusion to fit the aileron. Fortunately, the ailerons are shorter than the flaps, so the entire width can be satisfied with a single piece of extrusion. Then I clecoed the extrusion in place and final drilled the holes through the trailing edge skins, then removed the clecos to debur the skins, and then dimple them. Then I used the countersink cage to prepare both sides of the trailing edge extrusion to allow a dimpled skin to sit flush.
What's next? I think it'll be time to close in the nose section of the aileron by riveting on the bottom skin, and then setting up the adhesive on the trailing edge to cure overnight.