GM:
I think your post got lost among the others... welcome to the forum!

I think you'll find that it's NEVER recommended to "box in" a speaker. Since no one answered you regarding the mounting depth of the FMB, I would place a call to Axiom and ask; they're nice folks! \:\)

::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::