Here's what it looked like the day I made it:
The panels can easily slide on and off, depending on whether they are needed.
The modification happened just in time. I've been utilizing it quite a bit - both the rack, and the raised bed. This morning I had to get 11 sheets of 4'X8' subfloor sheathing. This is pretty heavy stuff. The Nissan took the load like a champ (even though I didn't - I very awkwardly tipped my cart over in the Home Depot parking lot and spilled everything on the ground: sheathing, lumber, bolts, caulk, etc...). I bought 2 new ratchet tie-downs so that I can secure my lumber properly to the rack.
Things to do:
1. add some hooks in strategic places along the sides of the rack to attach the ends of the ratchet tie-down to
2. paint the wood with deck stain for durability and water resistance
3. add a lock, so that I can store tools in the bed in watertight containers (?)