A little bit of bending, filing, or adjusting should free up the latch on the back glass (I take it is has one handle to latch both sides). There is probably some way to pin the latches with small hitch pins on lanyards to secure the latches from the inside. I have a Leer 8ft topper/cap/whatever you call it, and have never opened the windows. Truck is used to pull a travel trailer and back is loaded with griddle, patio mats, directors chairs, and a cheap 10x10 pop up gazebo.
They have not been called "camper shells" since the '70's that I know of but that used to be a cheap way of camping, but usually cold and damp.
Charles