I have replaced two windscreens in my 1961.
See Subject 1961 classic 22ft runabout for photos.
The bottom of each screen is solid timber cut with a jig saw to the curve of the same shape as the screen and also pliable enough to take the curve of the deck. It can be done with a number of pieces of wood so you don't have to start with a large rectangular piece to cover the whole area.
Mine are 1 inch deep 20mm to allow good bite as this craft can go quickly.
You could also laminate sections from plywood and epoxy seal to get your shape.
You would also have to chamfer the timber according to the rake of the screen.
A bit of mucking about but the result is safe and LOOKS good.
Mine are covered with aluminium strip to suit the boat but you could cover with timber veneer ,screwing it over the top
of the perspex.