Sounds like pretty standard for the time and suggests that one was built by Sam himself. There's really not a lot of stress there, so rubber bands are fine. I'm attaching some Saturn pictures for reference. Some are detail shots of the one that ended up with the late Al Weir. I can see that I used a 1/4-20 bolt from the fuselage inside through the wing end plate. The other photos of the Saturn with the Supertigre are of one of the prototypes I flew in team selection.
-Ron