Built a loft bed in the back of our Sienna out of unistrut. This allows us to car camp with minimal setup and saves on hotel fees for our road trips. Also shows how much room is gained by removing the third row completely. 20 minute install once completely built.
Dimensions are 49" wide, 52" long, and 24." in height.
We know this won't be for everyone, but it works great for us and has saved us a lot of money when in route to the west... for us, its two nights just to get anywhere... it has paid for itself so many times over.