What do you guys use under your LR?

[Son Of Skyline]

Like the topic asks, what do you guys/gals use as a base for you LR? Base rock? PVC? Nothing? I'm going to need to mount 100+ lbs of LR and I'm wondering what you all might recommend. To me PVC seems the cheapest, but can it handle all the weight of the rock? I thought about eggcrate on top of it, but I don't want anything like that to end up showing in the tank if a fish starts to dig under the rock. Suggestion? Thanks in advance.