Trimmed rib number 6.5. Yes, 6.5. That's because it's about halfway between rib 6 and rib 7. It's the rib that's immediately inboard of the aileron, and it's only from the rear spar to the trailing edge. It is fully sheeted and it has a hole in it to permit the aileron to connect to the torque tube and to fit in the bearing as the inboard hinge. Measured, fit, trimmed, measured, fit, oh, maybe I moved something there, better measure again. Finally, was satisfied to mark where the aileron connection passes through rib 6.5 and cut out and finish the hole for the connection. See pictures.
Again, after some more fitting and adjustment and fitting some additional blocking for spar caps, I epoxied the rib and the spar caps, into place.