Yes, I run long lumber through the window. With what you suggest and the extremely short length of the bed, the lever arm of 10 foot lumber would tilt out of the bed onto the road.
What is the point of having a "truck" that is not functional as a truck. Pray tell, for $80K+ how does one transport 2x4 lumber with a rear window that does not open. This is a deal breaker for me.