Those pieces of (probably tempered) glass aren't doing you any favors. Get a piece of acrylic and cut it on the diagonal.
Once you settle on the overall form, the final Cd figure will depend on the details — i.e., the radius of the edge. A hard edge is worst. The rule of engineer's thumb is radius equals 4% of overall width, or less than 4" minimum.
The sheet acrylic can be cold rolled (I'm pretty sure) so roll the hypotenuse and leave a flat triangular tab to fit in the lower front corner. Then rely on fiberglass to fill in the gaps.
I'd have to Google for a supplier, here:
https://www.google.com/search?q=fiberglass+sheet++stock
It looks like it's called fiberplate.