windscreen help ?

[snapper]

Oops just read your profile, you are a long way away.
The original "Build a Sports Car for under £250" by Ron Champion has a diagram of how to make the screen, personally I would ask Kits Parts Direct for the measurements of theirs.
The bottom rail runs along the scuttle and folds down the sides by a little.
I can read the problem you are trying to solve but describing it is difficult, I would do a mockup out of wood and cardboard, you will then solve the issues, next get the glass cut from a flat Landrover laminated screen, then make the screen surround fit that. Drill and tap any holes for fixing the screen or wet weather gear first.
I also put small support angle on each screen support for the screen to rest on, I did not like the idea of just 3 small bolts either side holding the screen on at over 100 mph.
To fit the screen I put bicycle inner tube round the glass edge and with some washing up liquid for lubrication I pushed it in, when the screen surround was bolted together and fixed to the car I ran a scalpel round to tidy up