What is a good way to build up and repair that wallered out hole? I’ve been thinking about welding a washer underneath the hole on the crossmember
That's correct Tom, but consider a plate of decent size that fits the shape of the area. 3/16 thick. You probably should bolt it all up and get it correct, then tack weld plate. Then if you ever need to take apart it will stay exactly aligned. Just tack weld, no need for mega weld. The welds won't add any strength anyway and tacks will heat the frame less.
