Originally Posted by JRock3x8
Think of it this way. If it doesn't work or if I don't like it, it's way easier to downsize than to go the other way.
Well, while I can't disagree with that mind think, the one thing that I do find error in is that when somebody or yourself know that such a course of action is virtually assured to result in less than desirable results, going ahead anyway is akin to sayin'... "I don't mind wasting my time."
They only go so far as to say that because the construction of a frame BB acceptable for a 150 inch + spandex screen is no small undertaking, nor a trifling expense, and with optimal performance in mind, I just have a hard time justifying both the additional time and expense because I know myself what the end result will be.
What I cannot know its just how far down the road into frustration that any given do-it-yourselfer is willing to travel, because for some the frustration index has a very high limit, and they're going to do what they have decided are going to do no matter what else is said. And that's okay under those circumstances because every once in a great while somebody proves that the conventional line of reasoning doesn't apply and that can be a very good thing for everybody involved.
Now while the projector you're using is well noted by many people to be a lot brighter than most expect it to be, you are out at the extreme limits of its performance envelope on a screen who's game factor is below what is normally considered acceptable levels. You already seem to have a pretty good inclination of that so at this conjecture the decision to go down the path you've chosen and the acceptability of whatever in results that you achieve, all falls squarely on your own shoulders.
It's a brave new world out there for those willing to take such risks, so have at it! And to hell with whatever anybody else says!
Of course I say that last remark with all due respect to everybody else.
All that being said, since you seem to want to sit as close as you do it would seem that you could go with a smaller screen and just sit close enough to make it seem like it was a larger screen. But if I read into your post correctly the real issue is where you have to place your projector, and with the particular Projector chosen that could be a real problem.
But perhaps not one without a solution. Recently my partner PB_Maxx has completed a sprayed spandex screen using Black Flame X1I. That application it's definitely going to have a higher gain than unsprayed spandex, and any increase in gain is going to work to your advantage so that is something for you to consider if the additional cost of the paint and the need to spray it on can be accommodated.