I would try to identify the cause. If your 1975 is the same construction as my 1974 (which I would assume it should be) there is an upper and lower fiberglass sandwiching a fiberboard inner layer on the floor. The floor could be sagging because the fiberboard has gotten wet and lost all strength and structural integrity. It could also be caused by twisting or sagging of the structure (the entire Boler
body) which can be caused by a bent and or broken frame. I experience the twist and deformation on my Boler
due to the frame being bent and the bolts securing the body were all missing or loose.