I'm installing a shed on some 2x2 patio stones in an 8x10 rectangle. The ground is not level, being about 4+ inches higher on one side than the other. I plan to put about 5" on 3/4 gravel and 2" of Limestone screenings under the patio stones to help with drainage/heaving. But I'm wondering how much the gravel might migrate if I don't put a border (PT lumber) around the outside? I did something similar a few years ago with some penny pavers and marble chips (same gravel base) and I used a PT border to keep the chips in place. It worked out well then, but I hadn't really planned to go to the trouble this time. Although with my slope it might be a good idea.
Any preferences?