I'm building a passagemaker take-apart and have filleted the transoms. I'm now trying to properly position the bulkheads and don't understand the manual's direction to measure in a 'straight diagnonal'. I interpret this to mean from the front right to the back left (or front left to back right) but when I also incorporate the measurement from the rear transom (on the bottom of the boat) the measurements don't appear to be correct. I've tried to understand this better by 'rough fitting' the rear seat as well and all my measurements are 2 inches off. Should I quit obsessing and go with the rear seat approximation?