KJay
So you feel a deduction should be made on Carlon boxes for supports in all but one gang which has none? The Carlon letter just states go to 314.16 which covers all deductions. You bought up something I;ve never thought of. I'v always felt the plastic taps in multigang boxes didn't count. I;d like to see what UL or others say about this. So you'd only count ones where romex was used? Or all. I;d say just where a Romex enters the box if at all.
Yoopersup