Is 1/4 inch (6 mm) plywood, glassed over, adequate for a non
load-bearing, hard canopy for my little cruiser? The canopy will be
about 9ft long by 6ft wide, and slightly curved for water run-off and
aesthetics. How many layers of fibreglass cloth would be needed?

I intend to force the plywood into shape and allow the epoxy and
fibreglass to keep its shape when dry.

I'm trying to avoid rafters as they eat into the avilable height.