cost of new window material and sizing query

[symondo]

Approx size of 4x2ft - give or take a few inches in both directions

what would you expect to pay for a window of this size in 8mm thickness?

Would you use Perpex? Polycarbonate? Glass?

Its an aluminium frame on a fibreglass structure.

what would the ramifications be of using 6mm instead of 8?

 

[C08]

I am no expert as many on here are but I have just replaced some of my wheelhouse windows, the front large one 28"x 55" in polycarbinate and the side windows 20"x45" in acrylic . My observations are:- 6mm polycarbonate sheet is much less rigid than Acrylic, it is much softer and scratches much easier than the Acrylic and it is not as perfectly transparent although both my materials were glazing quality and the acrylic is UV resistant for the outer facing side. In the sizes of your windows I would have thought that 8mm acrylic sheet would be good, 6mm would do but whilst you are doing it why skimp as it is a fair bit of work.
It may be than in the very long term polycarbonate does not develop stress cracking in the same way that acrylic will but you are probably looking at 15-20 years timescale by which time the polycarbonate may be so scratched or milky that you would want them replaced anyway!