Rough assemble the canopy deck. Glue in the formers. Now, what angle do you put the rear former? Align the rear former so it's parallel to the back deck. It does not have to be exact. Just close enough so you can glue in the stringers in place.

The sheeting was straight forward. Cut two pieces, glue them together with some thick CA. Immediately sand the joint with a sanding block, then flip it over and sand the other side. I cut about 1/2 inch off each at the rear, tapering up to the front. That way the side pieces glued in are at about the right angle to fit on the canopy deck. See pictures. I put a litle water on the underside of the sheeting and set it on top of the deck, with some books on each side, to help shape it generally to the frame.