The screws on my setup pass thru the block of wood, and go directly into a wall stud. You really need to catch a stud to mount these properly with the FMB.
Here is one other idea you might consider to try and minimize drywall work- If the FMB is going to fall between studs..
You could purchase two of those mounting kits (from home depot or something..) used to mount ceiling fans. The kit I am thinking of is a metal rod with threads, that allows it to unscrew and dig into 2 joists (when used properly), or maybe wall studs for our case here..you unthread the rod until it contacts the wall studs and digs in, but not so tight that it bows the studs. Then there is hardware that allows you to mount a recepticle box, typically used to house your wiring for the ceiling fan.
You just have to cut the hole such that the box fits thru, and then you screw it to the metal bar. THEN you could get a metal box cover ( or maybe make one out of some slightly heavier gauge steel)..drill it for the FMB, and bolt it up to the box you just installed.
Not as good has having a stud to mount to, but it will require minimal drywall cutting, and allow you some degree of freedom to move the location of the box/FMB within the studs, for centering purposes.
just an idea, have not ever seen it done this way
