I found the '73s wheel well lower tubs were best anchored to the shell and only loosely clamped between the floor and frame with a lot of evidence they had defeated all the asphalt weatherizing caulk tape moving with shell travel --- so they 'felt' solid. The top interior tubs were best anchored to the floor and only lightly attached to the shell. The gap between them was packed with fiberglass that amplified the 'solid' feel to them.
The gotcha a couple of us have found on shell-off's is the shell relaxes slightly in a curl (the end channels lose a couple of inches distance between them) and stretching the entire length of the trailer is a major hassle as the weight binds everything up once its resting against the floor.
Where I saw 'slop' the worst was the battery and water heater shell cut-outs where I had patched over them, what had been skinned over taut before pulling apart the shell/frame went back with an inch of bowing outward.