Check out the thread "Canvas Replacement on Pop-top". I have tried to update what I have been doing. I had to repair the lift mechanism as well.
I have done the sewing myself. The canvas that was on my trailer had four screen windows
in it and I decided to only do two. They are a pain to sew. I also am using waterproof rip-stop nylon. The top part of the 'canvas' will be attached using velcro instead of the original staples. The bottom part will be attached to the frame using staples and some molding.
All I have left to do is the cover for the two screen windows
Hope this helps.