At Menlo yesterday an 8-yr old kid sat in the back and closed the hatch. His head seemed pretty close to the glass when looking from the outside, but I couldn't tell how close really. He seemed comfortable enough, but I would cinch those belts down tight to make sure his head didn't hit the hatch when going over bumps. I guess air circulation shouldn't be a problem as there's a big opening to the main cabin and the volume of the rear hatch is quite large and deep. But if it's a very hot and sunny day will the A/C make it back there with enough volume? not sure