How to attach FRP for surface of kicker?

How are you guys attaching this FRP to your kicker? The stuff we have is .09 inches thick. Seems to me like it would be very hard to countersink a screw into those so there arent any heads sticking out to gash your board. Also, this stuff is super flemsy. I dont want to have stringers running across every 8 inches, but if I dont then the gap will be to big and I dont think the FRP will have any strenght. Is there something you guys are putting under it to add some rigidity? Like temperboard or something? Im just not too sure how that would hold up in the water.

Thanks