Stop in for a cup of coffee

Where did you score the rubber sheet? Did it have adhesive on the back?
No adhesive on the back. I got it from Amazon. I mistyped earlier, it's 1/8" thick. You could use 3M double sided tape on the back if you wanted to.

Amazon.com: Eco Pultrusions Roll Neoprene Rubber Pad, 1/8" Thick, 24"x36",Black: Industrial & Scientific