Roof deck tiles?

I recently purchased a house in north park slope and the roof is in need of decking to protect the membrane if it is to used. Roof deck tiles seem the smart way to go, but I’m scratching my head over the best tiles to use. The roof is surrounded by a masonry wall that is at the exact legal height for safety, so whatever tiles I use will decrease that measurement by their thickness. This height consideration is the main reason I am considering using a pvc tile from Greatmats (see link below), since they are only 9/16″ thick (vs. 1.5″ thick rubber tiles). The pvc tiles are also considerably less expensive and less heavy than the rubber tiles. My chief concern about the pvc tiles is that they are stiffer than their rubber counterpart and sit on smaller feet, and so are more likely to perforate the roof membrane (even though the company says that the pvc tiles are designed not to do so, and they have had no reports of the pvc tiles causing this sort of membrane damage). I would appreciate hearing any thoughts on this. Thanks in advance. http://www.greatmats.com/products/non-slip-flooring.php