I think the issue is often the straps are not set to be stretched enough, if they have good tension they hold the cover up, if they are slightly slack or no longer elastic the cover will sag. Rob, you posted some pics of these recently and i noticed they were sagging alittle, if they have to be stretched to hook through the retainer on the body.. and if the tennax fastener has to be a tight fit to get on it holds together quite well.