I keep my sleeping pad (insulated air mattress) inside my pack, to avoid punctures. If you must have your sleeping pad on the outside, this would be the exception to my rule to avoid stuff sacks or, if absolutely necesssary (like around my cooking pot to keep the lid on and the contents from falling out) to use the lightest available (lightweight silnylon or mesh). In this case, I'd use a sturdy stuff sack of polyurethane coated nylon to protect that pad. It won't be much use to you with a hole in it!