It might be interesting to hinge the top of the bulkhead to the tonneau in such a way that the tonneau could be flipped all the way to the front, thus enclosing the front instead of the back. (Assuming the bulkhead remains stationary.) Worse aero, but might be useful depending on the cargo you are carrying (it's hard to get to the front open area to load and unload stuff with the half tonneau in the usual position).
My half tonneau is smaller because I have a Rambox, and can be slid out of the Rambox rails, flipped over and laid on the floor in case I need the whole box. I did find however that it expanded enough when it got wet this winter, that I was no longer able to slide it into the rails. There's always something...
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