I propose to create an aperture into which I can place the windscreen, on top of PU, so that the windscreen is bonded in.
This will have less wind resistance, look nicer, be lighter and be less prone to leaks.
Any advice?

Hi Tony,
I think the only way would be a grp moulding with the inside aperture a bit smaller then the screen outside shape, that is then bonded onto the inside of the body aperture, which would give the step needed for bonding the screen in, could also be used to surface mount my oversized rear screen, can you tell me exactly what is the PU adhesive, if I can find I may give it a go.
John

You can get the correct windscreen bonding compound from most motor factors.

In the past I have used Sikaflex but Tiger seal or any of the other single pack moisture curing adhesives will be OK.

Removing the screen afterwards, should you ever need to, is a bit of a bugger though. OEM bonded screens usually have a heating wire embedded in the sealant so that it can be melted for removal.