Need advice how to install the cement board on face of the fireplace

[Rogerius]

We finished enclosing the FP30 fireplace. On sides we used 5/8 drywall and on front the cement board.
The issue which I have is with the cement board. The screws which hold the cement board are quite spread apart (distance between is the width of the fireplace) so the board is flexing right above the fireplace door. Any recommendation how to add one or two screws above the fireplace door? Can I drill and tap some holes in the area marked in the picture?

 

[DAKSY]

Looks like you need to extend the concrete board per this pic from the manual...

No fasteners are allowed in the area you specified so the fireplace can expand & contract with heating/cooling.

 

[Rogerius]

I was searching the forum and found couple pictures of different install. In this one actually I can see screws in that area.