Not exactly the issue you are having, but I did have an issue where my rear body mounts punched thru the rotted out tub. So I cut myself some access panels, cut up some 3/16" steel and welded the new material in to repair and re enforce the area.
What I started with
Then I of course welded the access holes back up afterwards. Hope this helps you a little to see what you are dealing with and how to address it
92 YJ. High Output 4.0L
Rubicon Express 4" Lift Kit, 2" Body Lift,15x8" AR 767s, 35x12.50 Xterrains, Home Made Snorkel, Sanden OBA, Home made rocker gaurds. 8.8 Rear with Discs, 4.10s F&R, ARB rear, Detroit EZ Locker front, WarnM8000 with Viking Synthetic Line, Beadlocks, Tons of Mods
Score: 682RRv1.0 with a BOA of 13.47
I'm now doing custom bumpers and lift installs in So-cal