I am in the process of adding an interior bedroom to my townhouse. One of the walls is a common wall and fire rated with two sheets of 5/8" drywall. Where I live Romex is code and not conduit. To minimize the cutting into of an existing wall, I want to use cut-in boxes. Is it within code to use these on a fire rated wall or do I have to attach a box directly to a stud?

Chris