My method:

I put the trimmed canopy in place with rubber bands just the way I would want it. I trace around the canopy with a magic marker (washable) I then remove the canopy and cut away about a 1/4 in wide section of the covering and some of the balsa so the edge of the canopy doesn't protrude. I then roughen up the area of the canopy that will contact the epoxy, and then put 10 minute epoxy in the groove. I then very carefully, very carefully, very very carefully put the canopy in place such that I will not have to slide it around. I then put the same rubber band back in the same place. Then I cover the canopys edge very neatly with the covering.