Originally Posted by couchguy
the problem with that is that the new box would have to be steel for grounding, I have to use a plastic box ( i have not seen a steel box that can be used for excisting construction)unless there is another way to ground it to the steel flex conduit.
There are steel straps available that are kind of like a double t shape to hold steel boxes up tight against sheetrock. Two legs of the strap go against the back side of the rock and two tabs bend over the sides of the box. The adjustable tabs on the top and bottom of the box bear against the outside of the rock. You should be able to find them at HD, Lowes, or any decent sized electrical supplier.