On December 8, 2015 at 18:02, Mac Burks (39) said...
Keep in mind that those mud rings want to attach to the box. You will most likely need to chop drywall to get the old one out and the new one in. Then you have to worry about the cover plate covering the new larger hole.
Right, and the custom wallpaper will be trashed.
The problem that's solved by the new single-gang 4" box cover is getting mounting screws in the center of the opening. Another way to solve that problem is to make some mounting adaptors.
For the metal-workers in the crowd, what's necessary is
Two pieces of steel per box, about 1/4" x 4".
These pieces have to be thick enough to be able to tap for a 6-32 screw.
Two holes in each piece, centered on the piece and 1 13/16" apart (verify this yourself -- the spacing is just slightly larger than that), large enough to pass a 6-32 screw.
Centered between those holes, thread a hole for a 6-32 screw.
Mount each of those pieces of metal as a strap between the existing device mounting holes in the box. Mount your single-gang Decora device to that strap. Mount the cover plate to the device.
There's a slight chance that this will all be slightly forward of the wall. If that's the case, bend the strap slightly so it's a bit further back inside the box.