[Richard]

TJ,
I am going to pass on what I experienced in a similar situation when working with Ron Skeen’s windshield problem in the Newell he owned.

The problem started when he had Newell replace the windshields and a new gasket was used. The windshield would then pop out at one of the outside corners. The issue is that the solid center section of the gasket was thicker than the old gasket, so that when the windshield was placed in the opening it was forced into place. The first flex of the coach would squeeze it out of place.

Given the three dimensional nature of the windshield and the location where it would pop out, Newell was trying to remedy the situation by removing fiberglass along the A pillar. That approach was not successful.

The real issue was that the horizontal runs above and below the windshield were too close together to place the windshield and the gasket. When the horizontal opening was widened, the glass and gasket went back into place no problem, except fiberglass had to be added back to the A pillar to close the gap.

I think you may know all that. Cutting the fiberglass structure could be done with many tools. My preference for safety and control would be a vibrating multi tool with a fine tooth blade. Do make a curtain to tape to the inside to keep fiberglass dust out of the interior, it stinks and will make you itch. IIRC, we removed about 3/8 inch of structure to get the windshield to seat. Kinda scary, because it’s lot of work to fix if you take too much. Of course, you don’t need to remove material from both the top and bottom, one will do. But the horizontal cut does need a smooth blend into the A pillar vertical.