To make a plastic model look good is no easy task. I make canopies by using two part epoxy, forming them into the shape (usually, I make cardboard template, (glued together much like an upside down ship hull) and the slightly overfill the cardboard template with the epoxy. Sand to final shape, after it's hardened, (I use SteelEpoxy), and I make sure I anchor a stick in the bottom for firm mounting. I then take a sheet of clear blister pack from something I've purchased and heat it over the stove. It gets pliable very very fast. At that point I pull it tightly over the sanded to shape. You get a great canopy and can really form the edges. I am sure there are other ways, but this is a quick way to produce an excellent canopy.