Depending on the chute you have just some large flat headed rivets do the trick. Make sure you can fit your rivet gun in there before you drill any holes in the chute, and poke a hot soldering iron through the chute holes and bag when in position. Put about 6 rivets around the back edge of the chute so the smooth chute mouth does most of the rubbing on the sail.
I always put washers on the back of the aluminum rivets so the washer jams the bag not just a distorted rivet. Then very carefully file smooth the heads of the rivets otherwise any small burr will wreck your sail in large winds.
Luke