Parts 2 & 3 are complete as she sits on the bench curing overnight.
Going to take the proper amount of time at this point. The seal surface where the damage was done had pulled away from center slightly during the welding process. Fortunately I know a fiberglass guy ( :) ) and had access to PVA (poly vinyl alcohol), the parting agent used on unconditioned or non class A surface composite molds. After repairing the opposite side I hit the gasket surface with PVA and used Devcon on the side needing to be built up. Tomorrow I’ll pull it back apart but it will now fit every tiny scratch, ripple, dent, or imperfection in the opposing side it needs to seal to. This is much quicker, easier, and will be more accurate than even machining a welded repair. It’s very much like a “splash” taken from a given surface in composite tooling.
I’m STILL not convinced it will work though! Time will tell, we’ll have to turn laps to gain any confidence in the repair lasting for the long term.
I have been snapping pic’s as I go, when it’s finished I’ll try to share them.