There is a plywood backer board in the wall. You can find it with a stud finder.
The backer board in the wall was too high for the mount on my TV. I screwed a piece of plywood to the wall through the existing board to make my own backer board. That is what I attached the TV mount to. I would think doing similar would work for you if your board does not extend down far enough for you.
Here is my
post on the subject when I did it.
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Scott, DW, and Identical Twin DS (12)
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