World's most efficient RV! Mods for sleeping in back of Prius Three

With front seats full forward and rear seats folded flat, there is enough length for a 6' 2" person to stretch out and sleep in the back of the Prius Three. 1) removed the rear headrests, slipped the shoulder belts from the clips atop the rear seat, and then folded the rear seat flat. (2) I stacked two plastic egg crates in the foot wells behind the front and rear seats. (3) I cut a 17" by 48" piece of thin (3/16") plywood and placed it on top of the egg crates between the folded-down rear seat and the back of the front seat. The plywood should be right about the same level as the folded down seat, so you can now put an air mattress and sleeping bag on that combined surface and sleep. We found it works best if our heads are toward the front seat backs and our feet toward the hatch as you have about 50 inches width in the center but less at the hatchback opening.
We also made screens for all 4 windows by sewing big "pockets" out of no-see-um netting; we left an extra length on the outside of each window and hold each one down with a strip magnet.
We purchased a "tent" for the rear and found that while it increases the airiness of the cabin, it was not necessary for sleeping as I could stretch out and sleep even with the hatchback closed, which I would recommend in bear country.

 

Sorry about delayed reply, folks! Here is pic of left side screens . They are just sewn "pockets" of no-see-um screen mesh (very fine grid for the mesh) that slide down over each window. The rear door screen is all the way down and is secured at the bottom by magnet strips or magnetic buttons purchased from A.C. Moore or Michaels hobby shops. I am holding the screen for the front door window so that you can see how it is just slipped down over the door frame and has the extra 3 inches on the outside that is used to place the magnets on. The no-see-um mesh is from Campmor and I used either 3 or 4 yards of it to make screens for all four windows. To make them, cut out a section of screen large enough to fold over the entire window with some extra at the bottom. Pin the screen together around the three basic edges of the window frame (left side, top, and right side. Sew those three sides of the pocket using a large zigzag stitch. Slip over the door frame and secure with the magnets on the outside. You can still operate the windows when the screens are on which is useful if you just want the windows cracked open a bit, but in summer we had the windows all the way down. Remember to take them off during the day when you drive the car, though, as they obscure vision a bit. Does that help?

 

That piece of plywood is awkward to store as the 48 x 17 inch size is a bit big for the trunk and we put all four plastic milk crates in the trunk whilst traveling. However, the plywood does fit quite nicely either up un edge just behind the front seats or lying flat on the rear seat. I like the latter position as it makes it far easier to slide things in and out of the back seat. If you are carrying passengers in the rear, however, you might have to cut it in two and join the halves with a hinge. That way you could fold it and it should fit flat on the floor in the trunk area. I have not done that yet, however, as I like the rear seat placement.

 

I found the plastic milk crates were light, robust, and easily handling, but any system of sturdy plastic (or wood) containers that stack to the right height would do.
I also looked at the Habitent and would have purchased it for sleeping en route, but at that time they only accepted PayPal. The one we have now has enough floor area for a table and chairs, and thus provides a "living and dining" area off do the "bedroom", which we like.