You can also use something (3/4" wood or plywood) roughly the size of the back baffle of the M22 mounted vertically to the drywall with good drywall anchors near the corners of the board . The FMB load will then be spread over a larger area and a minimum of 4 anchors. This would allow the reinforcing board to be placed anywhere and to "hide" behind the speakers. Properly sized, shaped and finished this could be quite attractive. The strongest type of drywall anchors will be molly bolts which have spring loaded metal clips which fold to go through a hole in the drywall and then pop open to be pulled flat against the back of the drywall when the screw is tightened. Mollies can only be used once because the spring clip will fall inside the wall when the bolt is removed again. You must also put the bolts through whatever you are fastening to the wall before you push the bolts with the spring clips attached through the holes in the drywall. Get mollies with screws about 1"+ longer that the thickness of the drywall and the board. This can be done easily and cheaply with a trip to home depot and a few tools.
