with my HTRoom being above the garage there is an opening on the right wall close to my front screen wall.

Its for access to the full house HVAC system. I want to place a "fake" wall there so that I can open it but still apply OC703, fabric and trim and make it seemless to the rest of the wall.

Has anyone done this?

Ronnie (http://www.avsforum.com/avs-vb/showthread.php?p=8434296&highlight=piano#post8434296) did a hidden opening for his equipment

Hello,
I did place a hidden door in my theatre. When I framed the room, I wanted a door to get to our equipment from behind. I placed a door with a pressure ball mounted on top of the door jam. Then mounted the door with room to hang drywall on top of the solid door. Trimmed it out so the horizontal seams were behind a faux column and the corner of the room.

A lot to digest. The results were good to those who dont know. Several folks have leaned on the wall and fallen. I would seek out expertise from a good trim carpenter. My brother in law consulted me.

Why not just a removeable GOM panel, floor to ceiling and larger then the door? If your fabric treatment runs vertical, it could easily be hidden and the OC703 could be attached to the door itself. You'd need to give some consideration to the hinge area so the door opens fully.

I think SandmanX had a pretty elaborate system too!