Thanks for the info chaps. I'm thinking fixed windows with slot. I'll take the plunge and have a go! :-)
As for the flyscreen - the intention isn't to make a Le Mans replica per se. More a period boy racer! I have a photo of a MK2 SAH Spitfire with this bonnet and a fly screen and think it looks pretty cool; I'm pairing an SAH Bonnet, a W&P fastback roof, Some Le Mans wheels and some period engine parts from SAH all available circa 1967 when my mk3 was built. - All very tastefully done of course :-)