You could always use a straight joiner rod and tube as long as you drill holes through the ribs in a straight line, i.e. not matching the dihedral. A cub shouldn't have much dihedral so that shouldn't really be a problem. The hardest part would be aligning the holes so that the wing goes together straight. Of course, as you have noted, this modification would require stripping the wing to perform the surgery. It's also not very easy to drill a single thickness of balsa without splintering it. Honestly, I would probably consider spending a few hundred dollars to build a trailer; especially if you will have other planes of similar size. Then you can store them in there and when you want to go fly, just hook up the trailer and go.

Brian