I am looking to spruce up my existing inground pool deck. Currently I have patio stones which are frustrating at best (weeds growing and uneven, hard to sweep). I am thinking about using these envirotile rubber tiles I can buy at home depot. Has anyone laid these in any situation outside? I am a bit worried they might lift up on edges and become a trip hazard or shift. I am told that they can simply be laid over my existing patio stones. Before I fork over $2000 for these, I wonder how well this project will turn out? Any advice?