Hi,
I just glued in my door sills… a painstaking process to be sure. What I discovered is that the door sills are flat but the shell of the camper is NOT! I intentionally did NOT clamp the forward door sill to the shell while glueing and filled in the gap with epoxy/cellofill glue. My theory is that the doors have the same curve to them since they are cut from the same panels. I also tapered the ends of the door sill where the upper “bow” and the lower “bow” meet, due to the roughly 3/32″ of filler and glass tape where the panels meet. I tapered the top of the upper sill for the same reason. I could have ground the glass away but did’ want to do that much sanding as well as the strength it would take away from the door area.the rear door sill shell is a LOT flatter so a clamped like crazy there. I will say, once fully worked in, the door sills fit nearly perfectly! I rounded the interior side with a 3/8 round over router bit.
One thing I have learned along the way is epoxy that goes on is epoxy that needs sanded off later! Tip: Take epoxy cleanup seriously, SO much easier to thougoughly clean wet fillet goo than sand it off later! 🙂