I have actually looked at doing something similar. Did you use any padding under the liner? Also, what kind of liner did you use?...

Very curious to know what you did and if you would do anything different as I would very much like to do something similar in my back yard.

Edit: Just saw the packing material for the PVC liner you used.... In the video it looks huge and the one I was looking at using is almost double the size of what you have. Hmm, curious now about the padding if you used any.