Isolated ceiling projector mount

The home theater room will contain a ceiling mounted projector. I decided to build a mount block isolated from the joists to ensure sound doesn't travel through the ceiling into the floor above. I used a piece of 2x10 and 4 x RSIC-DC04 brackets to fix the block to the joists.

The goal is for the two layers of 5/8" drywall to cover the block, without a gap. The projector mount can then screw through the drywall and into the block. I pre-drilled a hole in the block for the HDMI and VGA cable to pass through and down the projector mount tube. The blue electrical box will house an isolated receptacle and the green low voltage box connects to a 2" conduit that goes to the equipment area.