I learned a lot from my first ultra frame:
Blocks under the feet are necessary. (Used wood under my 18', using concrete patio blocks under the 26') They will sink after it rains a few times. Level the blocks with a transit. A friend lent us a laser transit, I could work on the pool alone when needed. Dig down, as stated, not build up. I Got a gorilla pad this time, it made it so much easier to get the wrinkles out when there was an inch of water. Still filling right now. We used a base of modified 2A, then sand, then the pad. Probably overkill, but we are setting up on the edge of a field, were worried about grass and bugs.