I don't know of anybody that makes top and bottom masking on a curved screen. It does not make sense to have such an animal. Top and bottom masking is usually used on 16:9 screens. A scope screen, not 16:9 screen is often times curved to make the geometry work when using an A-lens. An A-lens is not needed with a 16:9 screen, therefore you do not see curved 16:9 screens.