In my experience.......
.....velcro from B&Q is a waste of money for ribbing. I've been down that route, cleaned and prepared surfaces etc but still, the sticky is just not sticky enough. It lasts a week or so, perhaps even one or two nice outings in the sun but as soon as it gets wet, forget it the very next time you pull it up to clean beneath you'll really pi** yourself off for not taking the better option. That being ainless press studs or if this ain't the solution, in the worse case senario, use additional glue.
Buy it & Use it, then sell it and buy something bigger