Instead of just mesh at the back of the hole, use a small piece of
wood. Make the hole large enough so that a small piece of wood can be
passed through it. Support the wood with DW screws through sound
drywall a couple/few inches from the hole. Then fill the hole. You can
then drive your mounting screws into the wood also.

I'll try to draw he

| Pass piece of wood through hole:
|
_____ --piece of wood.
|
| -wall

Then turn so it's parallel to existing DW & screw through DW to hold
up the wooden pice:

|
|-|-- screw
|
|-|-- screw
|

--

Larry Wasserman Baltimore, Maryland