Yeah you're probably right about the foam for muffling audio. If you haven't seen 'em yet, check out Gunny's thread
here for a quad mounted go-pro. It's amazing. He sent me a link to his footage with the epic mounted on his helmet and the same footage from the go-pro mounted on his chest and to me the go-pro was much better looking video. I prefer the stable mount on the quad so it doesn't bounce with your head as you're moving.
As for the snorkel, I would like you to do that if you don't mind. Battlegun has an outty, I have an 09-X and we have another 09 Gade about to be part of our own. With Project-X underway, hopefully we will attract more can-am owners and the more technical write-ups like you are talking about doing, the more it will help. I would like to see it myself, especially if you're talking about doing some kinda stealth snorkel as I would like to do that on my own. Just be sure to take as many well lit pics as you can along the way to help folks understand how to do each part of the install.
Great idea Stray!
Buster