Truth be known - yea, a tank hatch is useful but not sure how much help it would be for solving OP's problem.

Looking at the pic (4Star60 - assuming that this is the OP's plane as it has a 91 4-stroke) the rear former allows for the removal of the tank. It does not need to be radiused if a tank like mine is used. You will need to pop the tank tray out, narrow it so that it will fit between the doubled fuse sides, and supported with balsa block the set the tray at the new level.