When I use velcro I use roughly 1/4 - 3/8" wide strips, any more then that is overkill IMHO. This allows for half the cover strip to be fixed, the other half free floating for the velcro.
Note: Use industrial strength velcro. What also worked best for me was taking some 3m Scotch Brite pad to scuff the mounting area, then mineral spirits to remove any remaining dust or body oils.