Now I'm gonna throw a wrench in the works! When you guys that have done your headliners, have you noticed the two bumps at the top rear of the metal roof? If I can remember rightly, they are about 8" towards the inside outer edges of the window, on the roof itself. I've been thinking that that would be a good place to mount a couple of sunroof hinges. With some holes drilled into the glass, (glass shops can do this) & mounted to the hinges, a couple of holes in the bottom of the glass could be used for mounting a sunroof lock mechanism. Maybe/probably two would be required. Around the body opening for the rear window, a 'bulb seal' with the 'pinch-on' vinyl covered grip could be used for the window seal. (I can get this in bulk rolls) Now, the window would open at the bottom a couple of inches, or removed totally, temporarily, when you feel like it. The headliner would have to be slightly modified to go around the hinges. Just thinking out loud.