What to put under Intex 18x9x52 XTR pool installed on decomposed granite?

[alekdavis]

Just bought my first AG pool (Intex 18x9x52 XTR) and not sure what to put under it. I will install it on the leveled decomposed granite (DG), in Sacramento, CA. The original soil under about 2 inches of DG is mostly hard pan (it's so hard that a small Bobcat could not level it). I was thinking about adding an inch or so of sand to level the gaps and cover the sharp DG pieces, but Intex told me they do not recommend sand. I see mixed recommendations about using (or not using) interlocking mats, foam board, tarp, Gorilla Pad or the likes, and I'm a bit lost. I do not want to spend more than $200 (the less, the better). What would you suggest? If using interlocking mats/foam board/tarp/etc, is there a specific brand (characteristics, like width) I need to look for? I keep trying to get an answer from Intext, but the only thing I was able to get is that they do not recommend sand and do recommend a firm surface (duh!). TIA

 

[Texas Splash]

Gorilla Pads are quite popular. So are insulation panels.

 

[alekdavis]

In case someone wonders about the same, I hand packed the ground surface and then installed (from bottom to top):

1. Two layers of weed prevention fabric
2. Ground cover that came with the pool
3. 1"x8'x4' R-TECH insulation panels (foam boards)
4. Thick tarp

Worked out well (at least, so far). Here are some pictures:

 

[Texas Splash]

Looks very good.

 

[kylerf150]

What are the dimensions from the bottom of the u-shape supports across the pool? I know the Instructions say it is 19ft10in by 10ft10in how accurate is that? I'm trying to figure out this pool will fit on my existing concrete pad. Or If the support legs are going to slip off, my pad is right at 11ft wide. Thanks