I've got the devour cover from silencer central and it tends to slip after a few shots . I've also got the silencerco covers they have two types one with velcro pull tabs like silencer central and the other has draw string . The draw string seems to hold the best .
The mirage is noticeable through my scope after 4 or 5 shots so I ordered a Burn Proof cover. It has not arrived as yet and was expensive. I noticed that the Backfire guy (Jim Harmer Backfire.TV.com) is now selling a very reasonably priced one though. He notes that it is not for sustained fire but for bolt guns it works well. https://backfireshop.com/products/backstrap-suppressor-cover