OK. I didn't tape anything up yet, but just some numbers for people.
These would be the extreme maximum sizes that would still allow for a small frame around the screen...
Using the maximum width I would realistically use (potential for another 2 feet wider in 2.35:1, but I fear that it will be too low for the 2nd row)
1.78:1 - 123" wide, 141" diagonal, and 69" tall
2.35:1 - 123" wide, 133" diagonal, and 52.5" tall
If somehow I could go that extra two feet wider for 2.35:1, I would get:
147" wide, 160" diagonal, and 62.5" tall
I also don't think that it will work well with the projector getting too dim and such.
Keep in mind that my previous theater had a 1.78:1 format screen that would turn out to be the exact same 1.78:1 image on the 133" diagonal 2.35:1 screen mentioned above (same height).
OF course, I start getting into fL (foot-lambert)issues at either of those big sizes (due to zooming and not using an anamorphic lens. Maybe something around a 128" diag 1.78:1 to get enough brightness...
So many variables.