Not a 5er, but I had the same problems with my Outback, no where good to put the lawn chairs except in the back of the truck. Attaching a hook to the wall not a good solution. The wall is a simple very thin panel with Styrofoam in the middle. Nothing solid.
My Outback came with D-rings on the floor to secure the rocker chairs that were originally installed. Although I was using them to secure some of the furniture, I went to my local Ace Hardware store and bought some more. 2 short wood screws into the floor and I had a great way to strap the chairs down. I do lay them down on the floor and not upright against the wall. Still, the D-rings could be installed anywhere, provided you have something solid to screw them into. And these little rings can take a lot of stress! But to simply hold a chair from moving, it just needs to be snug. I use bungie cords. Works great!