Just adding some thoughts from my recent experience on the inserts.
You can save some time by drilling the 3/4'" holes first, then glue in the inserts and finally, use the metal fittings as a guide to drill the 1/4" holes on the drill press prior to threading on the ribs. Then, only the 1/4" holes need to be placed with precision. BE CAREFUL THOUGH: the inserts on the fuselage end of the rear spar MUST be glued AFTER threading the ribs onto the spar. You could drill them and carefully mark the positions with witness marks to get them back in for gluing.
On the holes that were too close to the spar caps to drill 3/4" holes, I drilled 1/4" holes, then used a 1 1/2" forsener bit to make a shallow pocket in the plywood to epoxy in a stainless steel fender washer to reinforce the hole.