Brian,
That is very clever and one of the most effective ways to isolate the deck noise transmission. Not over the top. I will add that to my knowledge base.
I have found a use for a product in permanent layouts. It is 2mm floor underlayment intended for use under laminate or hardware wood floors. Its sound absorption qualities are very high, but it won't work well on top of the deck. It would be perfect for this application.
Thanks!
Well done!!!