The elastic is strong and it ties down to prevent the wind from pulling it off. Just make sure, to state the obvious, that the exhausts and cylinder heads have cooled before putting it on.
That is what I have for my Panamera cover and it flaps like mad in the high winds I get at my French house. It is at the very edge of a 1000 foot high escarpment and is the first thing the wind hits coming from the west/Rhone valley. The cover has actually marked the paintwork on my Panamera in a couple of places.
