I would be inclined to "bite the bullet" and use the aluminum plate that Winegard makes. I didn't use it on my installation (a fiberglass roof), but, on a rubber roof it would be a good idea. Heat softens the glue that holds the roof membrane down and any resistance in the roller will cause the membrane to stretch, ever so slightly, but, over time that stretching can lead to loss of adhesion, cracks and then leaks. Aluminum sheeting, while the same idea is not going to be thick enough, IMHO, to prevent that softening and by not screwing it down it will push and pull the membrane the same as it not being there. The heavy plate unit will block some of the heat and the screws will firmly anchor it in place against adhesive loosening and shifting from wind going over the roof. There are reasons why everything on your roof is screwed down...4 more well sealed holes are not going to significantly raise the risk of leaks.
