After having the installer excavate down more there was some gravel and roots that were from an old tree and old septic field. I ordered the armor shield to be put down as I assume it will help with any rocks sneaking up from under and causing me liner issues later. He said he usually puts the pad down first with sand on top as you will see the seems on the pad. Is this okay or should it be on top? Figure it will help either way but wanted input on people that have used it.