Although I heard of people ordering bigger at the time, the longest I could source was a 96x60 sheet. This limited me to a max of 96x54 for a diagonal size of 110.25 inches at 16:9.
However, I wanted to put a small portion of the material under the lip of the screen trim to help hold it down flat so I used a calculator, similar to this one, to figure out the height after losing .25 to .5 inch per side. I can't remember what I settled on, not that it would make a huge difference.
Screen Size Calculator No issues with sagging yet. I made a really tight frame of MDF boards, pocket hole screwed together. I probably went overboard with the bracing in the middle but more had to be better, right?
I used a spray adhesive to glue the material to the frame. You will want help with that part and since the material comes in a roll, you will want to spread it out and pre-flatten it for a while, if you have the room. I skipped that step but I recommend that you do not.
I ran the outside trim pieces across my router table to cut out the recessed lip that covered the screen material. I wrapped the trim in a dark black material so it took some test cuts on scrap wood to get just the right depth to add pressure to the screen but stay flat.
To hang it I made french cleats into the top rail in back (a simple 45 degree angle on the bottom edge.) You have to plan your bracing accordingly to leave room for a couple of good size pieces to lock down into the other opposing angle cleats boards screwed into the wall. Lays flat on the wall, is very sturdy and makes for simple removal, should a reason ever come up.
