You do realize that will be a 267" diagonal.
For comparison, using projector central's Calculator Pro, my projector is recommended for 111" at 14'. For every 7" of diagonal, I need an extra 1' in throw distance. So for me to even get a 267" size, my projector would need to have a 35' throw distance.
You will need a light canon to be able to project an image that large.
What I want to do is cover the whole door opening with the screen and then get some black Spandex to trim out the screen... This way my LaScalas will have an unobstructed path for the bass bins too. I will be going for a 150"-170" screen size. I noticed that Seymour has a 1.3 gain AT screen so I don't think it will be too bad as I am on a 1.1 gain Jamestown 134" screen now. I have also thought about going with 2 BenQ w1070 projectors stacked for 3D use. I think 2 of them stacked would be way more than I could ever need even with 3D. When we start building the HT room I will put the meter on the screen and see how it looks and then weigh my options to get the big screen as bright as needed.