Thanks. We got the measurements. Now we need to figure out how to construct the 3' high pony walls where they meet the curb. I would assume that the edge of the pony wall (where the door will be hinged) needs to be at a 45 degree angle to the curb, but the actual wall is at more like a 22.5 degree angle.

Actually the end of that pony wall needs to be absolutely perpendicular to the curb. Just as a door jamb in a door way would be, so should the jamb in the "doorway" of the shower. Also, 28" is fine for a shower door. Normally with a neoangle shower, you have the two 4' walls, then the two sides coming out from the walls will usually come out 12- 18", and then connect on the angle.

Speaking of knee walls, here is mine. I am concerned that the wall is not really solid. It has a little flex to it and this is going to be the hinged side of the door. The contractor said it will be really solid once the hardibacker goes on. The rough opening is 32" so we could add an inch or so to each side to make more the turns longer. I was also thinking about making the wall thicker with a storage box on the left side next to the toilet.

Which way does it flex? If it flexes front to back (like if you lean on it it wants to move into the shower) then putting hardibacker on won't do anything for that. If it wants to rack side to side, then it should help. If you're really worried and don't mind a little additional thickness you can add a layer of plywood to one side (probably the outside).

It flexes front to back. I know people do this design all the time, so it seems it should work.
The walls will have granite on the top with a groove cut for the glass to sit into. The glass enclosure is supposed to be frameless.
The other knee wall has a tub frame against it so it is very solid.