I didn't do the 321, in fact, I've never tried it yet. I've been successful just smoking them straight through between 220 and 260 depending on the amount of time I have. I smoked them with just a little bit o rub with no mustard at all. Today is a different story. Today I'm going full force. I have mustard, rub and hickory smoke on these baby backs with a heavy spray (no spritz) of apple juice and at 220.
Leo, those are some fine looking ribs you have going there.
In answer to your question about the piece you cut off-those are the rib tips, Skirt meat is the flap of meat that makes up part of the diaphragm. Most shops will leave it on and some will trim it all the way off.