I have a Jensen P12N coming and was considering a 3/4" birch plywood cab. Not knowing what size to make the cab my plan is to take the measurements from a Traynor YGM-3. Obviously I will be measuring only the area that houses the speaker and not the whole amp. Since it's a Traynor head I figured I'd also copy Pete's closed back cab design. Does this sound like a good place to start?