Sorry, just saw this.can you post some pictures of your gun ports please I need to remove somestuff from the for part of the frame aft of the gun port
They are not wide enough
Its an azazing kit
FWIW I think your issue might be ties to frame spacers you're using.
I have found my sp[acing required a few sizes to fit frame tops while in jig. Given this I have had zero frames altered for proper width, all checked from main plan sheet with inside calipers transferred to frames, virtually all of them have come out almost exact. Couple of them off maybe a few thousandths, evened up after planking by sanding.
Lastly, since my experience has been less than ideal as far as leaving planking short on the ports to allow lids to seal, I've planked right to the sill edges and will take some thin stock to lay in side , top/bottom in relief to give proper effect which looks nice and neat, especially when, likely, I will paint them red ocre.
Tim