Sounds great but for my app it will need to be either2 screens or a CineCurve(or CineMask/VistaScope).
Why? Here are some pictures:
Curtain fully closed:
Curtain Fully Open:
Curtain open to 2.40:1 preset with projected image:
This is a curved DIY 2.65:1 screen that I built at a cost of ~$200.00 equipped with a combined curtain/masking system with 10 AR presets. Prior to building the new screen, I was using the same curtain/masking system with a 2.55:1 flat screen.
I am not suggesting that you forgo the screen if you need a non-unity gain surface, but the curtain/masking is a totally separate piece of hardware that can be installed to work with any screen, curved or flat.