you are way too Critical on your MetalSkills IMO although the Cuts were not perfect to myself they looked good enough i’m a retired Woodworker and we “Cleaned Up” our cuts with Belt Sanders i imagine a Grinder could do the same thing on Metal ,heck a Belt Sander with the right belts could work onMetal as well if you have your Ace Welder coming in i’m sure they can Weld in the voids and nobody but you will ever know what’s under the Myers Body in all honesty i couldn’t imagine in the 1960s at the height of the Fiberglass Kit Cars being constructed in backyards. everywhere by non professionals how terrible some of those Vehicles were done and are probably still on the Road you at least appear to have CommonSense and Integrity. what’s the worse that can happen you need to Weld in some extra Bracing or Mending plates ?