Lumens are good, but the crux of the question becomes:
What will the primary aspect ratio of the screen be?
I have no doubt in my mind that for constant image height the anamorphic lens is necessary. There is only one projector in existence that could zoom in and out with enough precision to properly service a CIH setup.
That would be the very large NEC digital Cinema pieces , which NEC will not have hdcp cards allowed built for them.
You could have a 1.77 primary screen of roll down type with masking and then be over with. If you really want to have a flat unity gain screen that is the correct way IMO, as a fixed 1.77 screen masked top and bottom says: This is a 1.777 screen masked down. What I call vertical masking: a top and bottom panel of black fabric to me looks apologetic when deployed over the primary 1.77 screen.
You really want 2.35 to look as cinematic as possible; for non anamorphic projection on a flat screen the above solution is the logical one, drop down masked. For anamorphic anamorphic there are overwhelming arguments in favour of the more esoteric Torus.
Then there is MTF, MTF has been dicussed ad nauseum in these forums and it is agreed that 3 chip dlp sports the most in native MTF than any other projection technology. That is one of the two reasons 3 chip dlp creams LCOS, color prceision and uniformity being the other (with proper setup linear lamp sources-THAT MEANS FILTERED IF UHP or XENON).
But MTF is all about contrast and the perception of it at very high resolutions.
Put the perforated screen out on the front lawn for Thursday pickup, because the perforations are the enemy of MTF.
In this case having a non perforated screen of unity gain is good but you will need a very large and inefficient projector. But FLAT is still ok if you are not using an anamorphic lens.
With the TORUS screen you not only get gain without hot-spotting, that elusive quality that gives you the higest reality recreation factor, however if you are using an anamorphic lens then the TORUS becomes INDISPENSABLE.
A properly implemented anamorphic TORUS projection with low angle of incidence will exhibit an optically coupled projection with perfect focus, and no light spillage from the lens attahcment's innate pincushion barrel doistortion. The screen was co-invented by the same guy that co-developed the lenses for Cinema Use and has 5 oscars at home to show for it.
I have no doubt in my mind that the TORUS will be huge in very high end home theaters, once some get out into the mainstream.
There have been a lot of pompous flat earthedness thrown around this forum about the acoustical anomalies of the torus. Yes there can be such acoustical calamities, I am intimately familiar with many such theaters, and one home theater of my creation was definetely lacking in the acoustics department due to improper speaker dispersion. But most importantly, of those AMC movie theaters that are CINEMASCOPE only the later variety of floor to ceiling TORUSSES with stadium seating sound bad.
The first batch of up on the 2/3 of the front wall TORUSSES are the formula to be emulated for home theater, when used with D'appolito far field type loudspeakers in the front, and controlled directivity (D'appolito variants) for sides and rears, then we are looking at the best of both worlds Audio Video. I have succesfully achieved one Audiophile-grade Torus home cinema with large floorstanders flanking the screen. If I can so can many.