It's interesting that you bring this up now as I am working on setting up a similar setup, except with a G1000, ISCO, and a HTPC.
I just ordered a 180" 16:9 DaLite Audio Vision screen and I will be making a supporting frame to mount it.
My current setup uses a 138" 16:9 Draper M2500 fixed screen which worked quite well with the G1000/ISCO combo.
Even though I've looked at a 8 X 11 sample piece of Draper AT 1200 screen material (which looked pretty good)I haven't actually seen the DaLite AT screen in person, so I'm taking a bit of a risk buying it.
My motivation for getting the DaLite material was mostly monetary, with the Draper screen only being available in a finished frame for $4000+, the Stewart being even more costly, and the DaLite material (without frame) being less than $700.
I'll have to wait a couple weeks to get the screen up and to get my G1000 back from calibration to see how it works, but zooming out to the larger future size looked pretty good, even on the flat white back wall.
With your G15's extra brightness and the ISCO to boot any one of these screens should look great, and I have high hopes that the holes will be invisible from normal viewing distances.