I have built double wood stud walls (with 5 to 8 inches between walls) throughout the studio - should I be using RC on both of the walls - I am putting 3 layers of drywall on each wall.
The answer to your question is no. The double stud walls accomplish the same goal as RC -- that is, to isolate one side of the wall from the other. To use RC at this point would be redundant.
Wes Lachot Design