If you use the throw distance calculator at Projector Central (http://www.projectorcentral.com/projection_calc.cfm
) for the G15U with throw set to 19', it gives you the following ranges:
4:3 on a 4:3 screen: 97.3-150.8" diagonal screen
4:3 on a 16:9 screen: 119.1-184.5' diagonal screen
I can't verify that these values are the "real" answer, but at least it gives you hope that you're not locked into that 145" diagonal screen.
Yes, a G15 can light up a large screen--even a 145" one, assuming that you have excellent (if not total) light control. As for how that looks (a G15 on a 10' wide screen), I'll defer to others--I've never seen such a setup.
Stewart can easily handle a frame/screen that size--everything they do is custom cut, and their website has all the stats on max size, screen material options, framing options, masking options, etc.
Check it out...here's a sample page: http://www.stewartfilm.com/engineeri...creenwall.html
Microperf screens allow you to place your front speakers BEHIND the screen--microperf screens are essentially acoustically transparent (they do tend to roll off the high frequencies, but this can be compensated for). All commerical cinema screens are microperf--the front speaker arrays (e.g., left, center, right) are behind the screen. Some people hate microperf--it takes away 10% of your light output and it does require care in installation to ensure that no light "backsplash" pops up (it's not that hard, just make sure everything "behind" the screen is flat back or non-reflective).
The reason I alluded to the need for microperf is that having a screen essentiall the same size as your wall precludes placing the speakers around/below the screen--although you don't really have to have a 145" diagonal screen (it looks like you could get away with a 120" diagonal), doing so would easily eat up most of your front wall real estate in terms of speaker placement options.
I sent you a private message on this as well.