Bulgde

Bulged black water tank, I purchased a used RV that was on permanent site (upstate NY) with a sewer connection for 6 years.  Previous owner used the black water tank as a pass through, result the tank was full of “ITâ€? the bottom of the tank has bulged out so much probably from freezing during the winter that the bottom is now lower than the outlet.  The RV is now is another permanent without sewers, the tank is not cracked or leaking.  It is such hassles to get it clean I have do something.

Opinions appreciated on my plan; I am going put a large piece of plywood and square steel channel supports under the plywood, using bolts going through channel and plywood to the frame and gradually push the bottom up.  Any suggestions would be appreciated.