So, this is what a mahoosive size 6 Ducksback cover looks like on a 5m XS rib. At least 5 feet too long, but nothing a few judicious folds can't sort out.
The benefit of the larger sizes is the greater girth (ooer!) although still not likely to go over an A frame.
We tend to get three or four seasons use before the waterproofing starts to fail. This one is now relegated to dirt and bird shite duties during winter barn storage.