As I posted in another thread:
our pool fell apart last week and as of right now, I'm planning on replacing it with a new Radiant 24' round Metric. A different manufacturer had online instructions that had you leveling the ground, setting blocks and putting up walls like everyone else, but then cutting rigid foam insulation panels to fit, taping the seams, and covering the base of the pool, then adding foam cove.
I asked a technical rep at Radiant about this last week (the instructions for the Radiant have you wheel in sand before putting up the last panel, forming the cove and covering the rest of the base with a couple inches of sand). He said this would be a great way to do the base, so long as I'm careful to cut the outside pieces so that they get out close to the panels. He also recommended putting one of the bottom floor liners over it before putting the liner in.
So I was all set to go that route, but then I got to wondering about the long term viability of this approach. if the ground shifts at all (we're in New England) sand would shift with it, while rigid panels might not fare so well. I suppose it really only needs to last as long as the liner; I could always patch it up when replacing a liner.
I like the idea, both for the added insulation and the smooth installation, but not if it's going to be problematic within a few years.