"Wally" wrote in message
...
Noted. I was considering using machine screws through both the acrylic and
cabn side, with lock nuts on the inside so that the fixings can be tightened
enough to bring the layers of material together without compressing the
sealing material.

My windows are "surface mounted." I recall the builder saying they had to be
very careful to oversize boltholes a bit to allow for dissimilar expansion of
the fiberglass and plastic. Of course, I don't know what kind of plastic is
used, what the bedding is, or whether this was really a dream.

Good luck.

-jeff