Thanks maniac... The issue is this...Current neck fits great. Current mouthpiece fits great. Got new mouthpiece that is too tight and won't fit cork on existing neck. Thought I'd get a 2nd neck specifically for this new mouthpiece. Want to switch between old and new mouthpieces for tonal variation. If I change the cork to fit the new mouthpiece, I of course will be too loose on original mouthpiece - hense a 2nd and dedicated neck. Guess I'm looking for an educated guess from someone on what 2nd neck will blow nice and not likely cause me to change anything on the horn.... Is the neck tenon on the neck or on the horn? If on the neck, can they really be contracted. If you were going to use a 2nd neck on a mark VI, what would you consider and why? Selmer standard Silver, Selmer copper, those retro necks 36 or 54? Is there something you'd avoid? Thanks...