Hi John - sorry for the very delayed response. Between a wedding and an unanticipated remodel in our master bath due to water intrusion, the theater was on the back burner... I've just now begun efforts to complete the project. Here are some photos:
1. The original space (before we purchased the home)
2. The nook.
I removed the fireplace and "entertainment cabinet" and reframed the room and created a nook that could be used to place speakers behind a screen. In addition to the nook, I built a cabinet in the hallway (left side of image) for the AV components that is open in the back to the utility room. The screen support structure (the wood in the photo) was created from the select grade pine at Home Depot. My goals here were to create a system that could support a screen and surrounding screen wall while being compact and able to be removed in the event the home was ever sold.
3. The screen frame
The frame was created such that it could span the 12 feet without needing additional bracing to minimize the damage to the walls. The screen material (next photo) is attached to the frame via heavy duty rubber o-rings through grommet holes in the AT screen fabric. In addition, the design a 1x4 perpendicular to a 1x2 gave both rigidity and a channel for my CIH mechanism as the screen wall panels are 3/4" in front of the screen.
The screen material was purchased from SeymourAV and the grommet holes were DIY'ed. The rubber o rings were from McMaster and anchor to the frame via screws that serve as posts. The frame was designed accounting for the force exerted via the o-rings - thus slightly bowed at the bottom. With the screen in place, the free horizontal frame components are parallel and within 1/32 of an inch variance across the entire span - better than I had hoped for.
5. Screen wall
The screen wall attaches to the frame and covers the grommets and also provides a track space for the yet-to-be completed CIH mechanism.
This brings us to the present - still a few things to do:
1. vertical screen wall panels - these will be anchored to the upper and lower large screen wall panels (2 x 12) via magnets and will cover 5 inches on either side to create a 130 x 54 inch screen window.
2. Wall panels - I have cut wall panels out of OSB and will cover these with fabric. These will run along the side walls and come onto the screen wall 3-4 inches to cover the ends of the screen wall.
3. CIH mechanism - my current idea is as follows:
black AT material from SeymourAV will be loaded onto Ikea Turplur roller blinds mounted on either side of the screen (there is a small space specifically for this). The blinds will be attached to a sliding weight that will keep a constant tension on the system (thanks for the idea!). The AT fabric will be attached on the other end to a sliding frame that will use a small roller track to move within the channel space between the screen and screen wall. Spring-loaded detent stops will be created for the various screen dimensions. I initially wanted to have this automated but hand movement makes the system much simpler and, I think, less prone to failure. I can always add a Somfy motor or the like at a later point.