This is an area not to be skimped on
I put six layers at the base of the windshield and four layers on the top of our RV-6A slider. During several years of work required to complete the plane and over three years of operations (317 flight hours) including several transcontinental trips, the canopy fiberglass is flawless.
According to my log I spent six months and one day getting the canopy just right - time well spent. Be sure you trim the lower part of the external latch handle on the slider so it will clear the top fiberglass if you or anyone else tries to shove the sliding canopy closed with the trailing edge of this handle pointed forward.
Bob Axsom