I had 2 "L" shaped pieces fabbed from 16 gauge steel. I set them down on the existing channel so that they made a "[". Then they were marked and trimmed for size and fit. I drilled the stud holes and used a 3/8" fine thread aircraft nutplate in place of the missing stud. Then I used Cherrylock rivets (high strength aircraft blind rivets) to secure the new "[" shaped section in place.
I used aircraft rivets instead of welding because the end product is stronger and I don't have easy access to a welder. If anyone has any doubts about rivet vs. welding, try and find a metal airplane that is all welded. You won't find any.
If you have access to the proper tools, my fix will be really simple. If not, then maybe you can modify it to work for you. Instead of using a nutplate, you could tack weld a bolt in place of the missing stud. If you could find some steel pop rivets that did not pull the stem out when they set. You could use them in place of Cherrylock rivets. The rivet stem needs to stay in place to give strength to the rivet. The stem in the rivet makes it solid and not flimsy and easy to shear off.
It may be that welding the "L" shaped pieces in place one at a time would work. Cut and fit one "L", drill the bolt hole and the weld a bolt in the hole that is for the missing stud. Then weld it in place. The repeat the cut and fit of the next "L" and weld it in place.
