Here's how I'd proceed . Cut a timber to fit in the tank saddle, run two straps around the tank, hook an air line to the petcock with a pressure regulator (not a valve), block fill cap, pressurize tank to about 10PSI, heat dented area with a heat gun, apply hot glue PDR tool, SLOWLY increase air pressure while simultaneously pulling with PDR tool.
The heat will soften the rubber tank liner and relax the metal. Applying pushing and pulling force will give you better chance of success. But remember to keep the air pressure low. You're not trying to blow the dent out with pressure just use it a helping hand.
The heat will soften the rubber tank liner and relax the metal. Applying pushing and pulling force will give you better chance of success. But remember to keep the air pressure low. You're not trying to blow the dent out with pressure just use it a helping hand.