I will be putting in a small wood shed this spring and I want to put down a stone pad first. The shed will be 5'x8'. I want to frame the pad with 2x6's. This will make my 40 sq foot pad..............Question...How many yards of crushed stone will I need? Also..Do you guys think I can get away with 2x4's instead? The shed will be 7' high as well....Roughly 6 face cords I will be able to put into it. Total wood weight will be 4500 lbs.