Make your diagonal strut with small bends at the end so they line up with the main legs. Grind the contavt points at least flat if not a little concave. Polish all the contact areas with steel wool or fine sandpaper. Wrap with uninsulated copper wire. Get silver solder at your local hobby shop or ACE hardware. Flux, heat, solder. Hints here:
www.smilesandwags.com/Floatsite/FAQ3.html