Built my first AG pool. Wanted to do foam coves and Gorilla bottom to save "time" and save the liner. Total cost for my 15x30 for both was around $300.
Foam cove - Not recommended. Was easy to build but only gave about 3 inch bottom/side coverage. Self adhesive backing was nice but in hot sun during install, constantly came off and had to keep pressing on. Was very difficult to keep cove piecese flush against one-another. When liner was installed, any gaps between sections became pronounced and I wonder if the liner will push through?! My pool is oval and the straight side aren't straight but curve in and out the the cove didn't follow very well and had to keep pressing against wall. More work than it was worth. Next time will try just using sand.
Gorilla bottom - I would not use again but I can't say not to use it. It was good quality material: thick felt type. It came plenty big and had to cut so no worries about being too short. However, could not get the liner to keep it flat. would pull flat and them where creases were seemed to pull in. I put in liner and started to fill. Still couldn't get flat and then it would not move. Did make and smooth surface but had ridges here and there. Overall nice product but very difficult to put in correctly. It seems sand alone would allow for a smoother more even surface.
My two cents worth. Please feel free to ask questions and I will give more detail. Thanks again to all who helped me build my pool at TFP!