We have some 1/4" thick rubber here at work, just cut me a strip 48" x 5" to try this out. I think this is a great idea, should cut down on dust and noise. Both are factors for me, we take my daughter and her friends riding all the time, should make it more enjoyable for them.
BTW, those little pockets behind the seats? that is where I store a couple of tow straps. Just roll them up tight and jam them in there (one behind each seat), they don't fall out. Always there in case you need them, never have to remember to put them in. Because we all know, you never PLAN on getting stuck, it just happens...