An excavator is not the way to dig a pool, a bobcat it the only way, the excavator has a smaller bucket and is made to dig holes and trenches. I use a bobcat, a rotating laser, and a shovel. I see no reason to get the pad within an inch, just get it close, the perimeter should be right on where the pavers go, the purpose of the sand is to fill in any inconsitencies and provide a "cushy" bottom for the liner. For my pool, I used the pad that goes under the liner, and I really like it. My first pool did not have one and there were footprints under it.