[CaptainPalapa]

I don't have a direct opinion about your question, but I would VERY much like to see you chock those wheels more so than you have now. Some good RUBBER (not those junk plastic types) wheel chocks, like you can get at Harbor Freight. If that were my rig on that driveway, I'd chock each of the four. While I *do* like your wooden gizmo, it could easily slide on that rock/tile/surface. Maybe a rubber pad stapled or screwed to the bottom could improve it.