My screen is 12 ft W for 2.35 (and thus ~61" H); for 16x9 (actually 17x9 for my Sony VW1000) it is 136"x72".
The light absorbing material is ProtoStar material (used to line telescopes; check its website), and I attached with push pins since I first put it up temporarily, just to see how it would work; it worked so well that I've simply left it this way; very simple. And yes it is REMARKABLE how much it enhances contrast, even if you have some external light (which I usually don't). According to reports on the Forum, you get the major effect if it only goes ~ 4 ft from the screen wall, but in my room it made sense to bring to out further.
With your size screen I understand that you don't have brightness falloff with the HPHC, so it is a more viable option for you. However I do note that the HP2.4 material is EXTREMELY artifact-free; it is creamy smooth and just 'disappears'.
Not hard to believe; as per my previous calculations: ith my curtains out 2ft from the wall it boosted the contrast around the edges 22% for a worst-case scenario image (all white, with one small black square). 9% at the center (which is less affected by scattered light).
I imagine the effect would be even higher for HP material, which'll scatter more to begin with.
Using your push-pins, were you able to keep the material pretty tensioned on the ceiling/wall? So as to avoid it drooping? I suppose if it were tensioned & flat on the ceilings/walls, it'd look more acceptable to me. I see I can also get the 0.04" 'FlockBoard', which I assume would be nice & rigid? Tack that to the ceiling? If it's light, I may be able to get away with a few small nails in the ceiling & some neodymium magnets...