Never really had a problem. The mats are heavy and they go over the side. Also the deck is enclosed more or less by the house so doesnt realy blow. 4th side is open unless I close the curtains 😉. Suggestion for the mats though why not use those plastic tie things, can't reber what there called. It takes 2 seconds to put on and after YT take a scissor and just cut them off.
If you hold maamid b'davar hapasul l'schach will pasul the schach, and that holding the schach down from the top (as opposed to resting the schach on something) is also maamid, then it's a problem.
My solution is to place bamboo poles on top of the mats along the beams supporting the schach, and then use the plastic cable ties around the beam and the bamboo poles, thereby sandwiching the mat between them. This would make the cable ties maamid d'maamid at worst which is mutar (AFAIK, except for the Chazon Ish who assurs even that). Only problem is that this is relatively annoying and hard to do (don't even try without gloves, you'll kill your hands).
