Why not install the electrical box alongside a stud and screw the side of the box into the stud.
Old work electrical boxes
I am looking into running dedicated AC lines in my house which will require the use of old work electrical boxes, also called remodeling boxes. Since this type is supported by the drywall only, are they strong enough to avoid drywall damage when plugging or unplugging power cords into typically grippy audiophile outlets? Does anyone have a favorite brand that has worked well for them?