I've been trying to get sufficient area coverage for a drum pad. It's not easy.
I saw an acoustic video of the Alesis setup and I was amazed how loud it is (without electricity).
Looking around, I see that you can buy piezo film in large sizes (like 8.5" x 11") but it's expensive! ($150)
With a top layer of rubber it would be a good way to come up with a drum pad that's as quiet as a practice pad.