Knightfly, will this work for access to pipes

Steve, I am planing on hanging 2 layers of 5/8 on RC from my ceiling. I have three shut off valves that I am going to need access to. If I frame a box around the area that I need to access (droping it down about and inch from the joists) and then cover it with two pieces of 3/4 inch plywood screwed to my new frame, will my isolation suffer much? Thanks, I included a pic. Craig

How 'bout something like this? Note that the fasteners for upper cleats pass THROUGH the RC and gypsum for best holding power ... Steve

I redid my plumbing to move the shutoff and drain valves to a place outside of where the room was to be.

Definitely a better plan, if you have that option... Steve