I also have an Angola cover. I use 1/8" dacron line, and a taut line hitch to the trailer frame. For years on a number of boats slipped in the water, we made sand bags, which attached to the points where the straps or lines would tie the cover down. I would probably add a "common sense"--this is the turn the tab type of fasteners. To keep the cover in place just in case of a heavy wind.
My cover almost covers the accent stripe on both sides--I shift it slightly to the port side, thus fairly well protecting the accent stripe on the Southern side. I agree that ssobol's idea to add fabric to the side will give better protection. But with the boat in the water, you don't want the be near the water line..On my cover 6" more on each side would have been plenty.