The Kloss was not a TORUS, it was a section of a sphere (like the Vutec in the other thread), the problem with the Kloss was that the projector was so dim that screen had to do all the work and you got comparatively bad results. Where did you see the Sony CRT? As far as I know there are *very* few TORUS installations in home theatre applications (and I think Peter has probably tied up more than half of them). The screen may have been curved (it may even have been curved in two dimensions), but it may not have been a TORUS. The TORUS CCS name really reflects the design work that went into the screen as well as it's distinctive shape.
The answer is: it depends. http://www.avsforum.com/ubb/smile.gif
Different types/brands of screen surfaces have different fall-off characteristics and require different curvatures. It also depends on how much light you can afford to lose in the corners, for example if you were willing to accept 10% brightness loss in the corners you might be able to bump the gain up a little for a given curvature. It also depends on the seating positions of your audience, if they are very spread out you will need a larger curvature radius and a smaller gain. There's some justification to the design fee that Sigma charges, a lot of experience is involved. How much light loss in the corners is acceptable, how much will give visible hot spotting? The math required to determine the curvatures is not insurmountable, but I doubt many people have the experience to determine the other factors involved.