OK, think I understand now. Here is how I would try to fix it. Get a good straight edge and some kind of jack. I would probably use a hydraulic bottle jack cause I have several, but a scissors jack or screw jack would probably work as well. Get the edge that has "sagged" top dead center. On the inside of the tank below the TDC edge put some shoring like 4x4 or 4x6 etc. to distribute to load and get the jack closer to the TDC edge. Put some more shoring in between the top of the jack and the TDC edge (like a short 4x4) again I think you want to distribute the load. Carefully jack a little at a time and use the straight edge to monitor progress. Bet you can get it back where it needs to be pretty quick.
Weber 26.75 OTG w/CI grates & SJ/WSM Mini
Home built 24"x72" reverse flow stick burner trailer with 18"x44" grill w/CI grates and upright SS gas oven/smoker.
Home built 48" fire pit with a 30"x30" Santa Maria style ranch grill.
Home built lump charcoal retort, iGrill & a bunch of other cooking toys.