I want to add a fixed window on the fore part of the cabin, so I can
see through the cabin whilst seated at the helm.

A tall cushion might be as good, but being able to look forward from
below counts, too. Maybe a bent plexiglas cowling trapped under the
partly opened fore hatch?

The forward cabin bulkhead is curved in one direction, radially
around the mast, so to speak, but not so much vertically. I have in
mind to cut a hole, then flex a sheet of plexiglas, whatever,
bolting it through. I wonder if 5200 can be trusted to never need
replacing, is good enough, too good, or if there are alternatives I
have not imagined?

Terry K