Well, I've done some more viewing of the HCHP and new White HP samples, placed at the 4 corners of where my intended screen (128x72) would be. From my sitting position, there is noticeable variation in brightness of the HCHP at the 4 corners, but not in the White HP. And in contrast to observations of some others, the White HP is slightly brighter than the HCHP; but this would not be a concern, it is the brightness variation that is.
I.e., the narrower viewing cone is an issue for my arrangement (described above). Since I have black fabric on my ceiling and side walls out about 7 ft from the screen wall (and also, of course, on the back wall), I don't really seem to have any issues with reflected light. (I don't with my present 119x62 HP2.8 screen.) I would get a 2.8 White HP in the larger size if it were still possible.