Though I have a man-crush on Chris MacCluggage, burn this into your brain: Don't get the Mashers. You have been warned.
I have ridden a ski with Mac Mashers and they are garbage.
Get real footholds, cut them in over the winter. It's more difficult but you're waaaaaay better off in the long run.
I run Rickters on one SX-R, WaterCraft Factory on the other, and WaterCraft Factory on my SuperJet.
Good luck and remember that we're here to help if you need it. I would cut into your tray with a multitool. I've used a dremel, a reciprocating saw, and a rotozip to do mine.