Innovative MarineSnappGrid eggcrate - (2) 10" X 7" + 8 Stackable RISERS

Can these be used to elevate/hold heavy rocks in an Aquascape as a base level in the aquarium, without the feet?

What kind of plastic material is it made of? Does it affect water quality

How tall are the pegs?

What is the length/height of each peg? With one peg and the egg crate what is the height? I need to raise my skimmer 1”.