I had an interesting conversation with Phil Sayers today in which he described to me the method by which the original windscreen for the Nova was produced.
What they did was get a metal worker to make a sheet metal template that fitted exactly into the aperture of the screen rebate in the canopy. This was beaten into shape to produce a metal blank that exactly matched the shape of the gap in the canopy that would accept the finished screen,
The metal blank was then heated and a sheet of glass placed on top. The heat of the metal softened the glass and allowed it to sink and conform to the shape of the metal blank.
Sounds easy when you know how, and I imagine this is the method by which triplex still produce screens today.