I have this really nice picture in my head of the system that our local Mike Haverly uses, which I think he copied from Paul Walker (one of them can chime in -- I don't know for sure what Paul uses).
It uses three aluminum carry-through stub spars in the fuselage, one at each spar location and one toward the trailing edge. The stub spars are drilled and threaded, and engage with aluminum shoes (sockets? ends? dogs?) that are glued onto the inner ends of the spars. The shoes are drilled for a machine screw with a "U" slot to the outside of the wing. You drop in a screw, then screw it in and tighten it with a ball-end wrench.
It looks like it uses less material than the one shown so far, and it looks like something that can be done mostly with lathe work and minimal milling machine work. Pick your poison -- I hope someone posts pictures, and maybe clarifies things if I'm spouting misinformation.