I also did corner gussets on my lower tubes where the engine mounts on a horizontal plane and both down tubes.
So far it all help except I just found a good crack on the left side swinger mount just like you have in the first picture.
Also, the seat latch bar needs reinforcing.
Also, the seat latch bar needs reinforcing.
If I had to do it all over again I would have made it a 3/16 plate than that thin metal that there.
great idea! Right now i have a couple of cracks on mine.