It was a matter of cutting away cardboard at the top to get the contour correct as the windscreen goes under the leading edge at an angle. Additional cardboard was added as I accidently removed too much initially. Much easier to do it now than to find out when cutting a sheet of Lexan. The final template measures 48" x 36". Will order a little larger just to be safe.
(Excuse the mess. The work area will get a post Christmas clean up)