except on a boat its BS. Measure twice, cut four times, shave a bit off, and finally in desperation hammer into place. On a boat there are no right angles, just a lot of wrong ones. The holding tank is going in, whether it wants to or not.
The original location of the sonar from hell, ideal place to put a 13 gal holding tank.
Dry fit, looks good.
Cut the remaining liner to discover that the lip of the forward water tank (which may be removed later) gets in the way.