Hi, my biggest problem with pool pads is that they are so thin. Every lump, bump and rock under the pad will show through when the weight of the water is on it. Using sand is a way to create a smooth base for the pad. The problem with that is it takes so much work to get the pads adjusted and taped into place and lot of footprints wind up in the sand. When the pool is full you see everyone of them. When using sand you would want a very thin layer of hard packed sand.
The best jobs I have done using pool pads have been either on concrete or in pools that have been up for a few years. After a few years of being under that much water the hard packed sand surface is ideal to work on.
When I am not using a sand base the option I like best are the 4 x 8 sheets of Styrofoam. A foam base, anywhere from 1 to 2 inches thick, and preformed pool cove around the edge makes an ideal bottom. It is easy to get smooth and very comfy on the feet.
Since the cove will go on top of the foam sheets, be sure to get the sticky back kind, and not the kind with the hard plastic for mounting into the bottom track. Anytime you have a track to work with I much prefer the hard plastic backed, more expensive, kind. Just not over foam where the track has been covered.
Dennis
PS I know a lot of people that opened up there Gorilla pad and immediately sent it back, they said it was nothing more than a heavy piece of fabric. The times that I have used it it has been next to impossible to get it to lay out smooth. It seems to be packed full of creases that won't go away. I have been much more impressed with other types of pads.