I agree this kind of tool is useful when one-man rigging, and this approach is very elegant. As an alternative, for the past 20 years I've used a 1" dia. length (about 12"-15") of Delrin or other hard plastic rod (i.e., anything softer than the bore of the spar bushings). When the wings are close but won't quite slide together, I just shove the rod into the bores and lever them the last bit. Obviously this won't work unless they're already fairly close but none of the eccentric tools will, AFAIK. The old Libelle 301 assembly wrench was the exception for two reasons: it grabbed pins glassed into the tops of the fork-and-tongue spars instead of fitting into the bores, and there was no turtledeck fuselage to get in the way so you could get a really wide angle with the wrench. I've seen guys try to lever 301 wings together when the pins weren't even quite engaged (unwise)!

Chip Bearden
ASW 24 "JB"
U.S.A.