I deviate from the manual all the time. Mostly it’s to streamline the build. The biggest example is I had the roof box installed and fiberglassed in (from the outside) before ever applying the 2nd epoxy fill coat. I did the fill coat on the roof box while sanding the first fill coat smooth. Did that a week ago, and only just last night cut out the galley hatch. Next up, door windows. Not the doors. I’m doing that so I can install the stiffeners and window sill (forget the official name) before cutting the door out in the hopes that everything fits later. I think one of the big problems with the doors is due to how many clamps people are using. If you squeeze the door to another part that doesn’t exactly match it, two things happen. The parts change shape, and you squeeze out all the adhesive. You’d never do that in a woodshop, so why do it when building a camper?
-Bob