I had a potential client ask me to lay a ~600sf patio/walkway of pea gravel with flagstone spaced 2-4"' apart. There is an existing parking area of 3/4" trap already compacted there. My question how stable is the flagstone going to be in a "natural" formation sitting in pea stone? My thoughts are the pea stone is going to shift as well as heave in the winter. We get some good frost heaves here.