Now, don't let me scare you off. The Sony isn't so dim, as to be not viable in such circumstances, it's just a little bit thin on lumens. In fact, on paper, the VPL-HW10 measures just about the same lumens as my own JVC RS1, which I have been using for a year and a half. Not sure why, but my JVC does just a little better than the Sony. I was concerned about my sports viewing when I bought the JVC, for the same reason, and while it does a satisfactory job, I also wish the JVC had another 25% or more lumens in brightest mode.
When watching the Sony for football, I've been keeping the image size a little below the full 128" of my screen, about 115 - 118" diagonal. At that side, it's doing reasonably well.
Since black levels are extremely good on the Sony VPL-HW10, a high contrast gray surface, like my Firehawk, isn't necessary, although if you have some side ambient lighting, those types of screens can help by "rejecting" the ambient light coming in from the sides. Of course, black level fanatics, may still want to go HC gray.
In my testing room, the HW10 looked really good on my 1.4 gain (Carada's claim) white surfaced, Carada Brilliant White. Blacks were still very good, although I had to drop the Sony down into eco-mode, as the projector, for movie watching, was a bit bright, even for me, and black levels of course become more noticeable if your image is very bright.
If you are a movie only person, figure you can go up to about 128 inch diagonal, without problem, however if you are someone who plans to watch sports and TV with some ambient light, the projector doesn't really have the muscle for a screen that size. As a result, I'd say, for mixed viewing (with some ambient light at times), you should stick to 118" or smaller screens.
To reiterate, the HW10 doesn't demand a high contrast gray surface, but, assuming brightness is otherwise handled, you can certainly consider a HC gray. I took a quick look at my 100" Elite HC (light) gray surface, and for movie watching, preferred it's handling of blacks over the Carada solution, but unless there is that side lighting issue, the Carada had a distinct advantage for sports and HDTV viewing, thanks to the extra gain.
