During actual usage I have a strap from the roof hook right above the rear side window and one from the grab handle above the 2nd row seats connected to the top pipe that helps stop it from shifting sideways. One middle leg is put through the rear seat latch loop that helps hold it in place. Lastly, the drivers seat is tight against the rack holding it tight in place. The top of the drivers seat and head rest, work fine to stop anything from moving into my body space plus the heavy rubber straps I use to hold the tubs in place. I thought about shifting items in an accident and decided to put my lightest item directly behind me on the second shelf and then live with the flow similar to what would happen if items were just setting/stacked without organizing. Across the whole rack I always put the heavy stuff on the bottom (water, recovery gear, etc) and the lighter stuff on top (clothes, food, pillow, etc.)
The whole thing cost ~$50 and the only "adjustment" I had to make in actual off road usage was to put a little pea sized clear rubber "foot" on the 2nd row window where the PVC was just close enough that it could tap on the window now and then. I hate extra noise so I shut that down in a hurry.
