Here's what I'd do, hard top and sides with no canvas....cuz, bears. Plus durability issues with canvas. The 5° sloped top is all it takes drop drag to near ideal and reduce the Lift Coefficient to ideal. The bottom has some odd angles but nothing really different than what you originally planned. The tops curved section is challenge perhaps.
I figure a flange on the bottom shell exterior that the top rests on when lowered, if the geometry is done right, the front could be lifted and locked in place then the rear so it could be done manually for simplicity.
The height is similar to yours, except a bit taller in back when raised.
Just a rough draft, we can talk more if this seems doable.
