I have a 2x4 studded wall that I will be covering with 2" rigid foam boards. I was thinking of using face mounted electrical boxes on the drywall. I would feed the wires through cut outs in the foam and drywall, and into the box. I would seal the wire entrys on the back of the box using mastic? acrylic caulk?, then put the box against the drywall, tighten it against the drywall and caulk around it. Is this the best way?