How I attach the ring terminals is:

I solder the terminal to a piece of 3/32" or 1/8" music wire.

I leave about 3/4" - 1" of music wire after the ring terminal (or more depending on the size of the plane and the load that will be placed on it).

I bend the ring on the terminal 90 degrees (or what is needed to mate up with the wing surface)

The part that sticks down I attach to cabane. In your case, you would need to drill a vertical hole in the end of the bar stock to take the piano wire. Make the hole slightly oversize and put some JB Weld in the hole with a toothpick. Rough up the music wire a little and put some JB Weld on the music wire and insert in the hole. Align the ring terminal up with the blind nut and let dry.

I do this all the time for struts and cabanes and I use K&S aluminum streamline (teardrop) shape aluminum. Depending on the size of the plane you may want to JB Weld a longer piece of wire into the bar stock.

I have had some "unscheduled landings" with a few of the planes, and while the tubing bent (and in one case the plate ripped out of the wing), the JB Weld held the wire and ring terminal as if it were actually welded in there (the struts were "functional" struts). If you do try it, use the original formula, not the 10 minute stuff.