Still trying to build the chops. I find that after a tem minute warm up of low tones and octave slurs, my mid staff notes have a fluttering that I really have to concentrate on to stop. I have been using a Bach 5C and today, I tried the Bach 7C that came with the Yamaha 2320 I use. There is no discernable difference that I can tell. Will this go away with practice or do I try some other MPs?

Bruce,
it will go away after a while. If you hold a heavy book out at arms length for 5 to 10 minutes, your arm will also flutter after putting it down. Practice brings stability of breathing (airflow) as well as stability of embouchure. You still have a little way to go.

Rest as long as you play, soft long-tones , lip-slurs, scales ,with plenty of rests in between each group, approximately 5 minutes on 5 minutes off.

It sounds more like you've got an airflow consistency problem rather than your chops. If you can't actually feel your chops moving (the corners, that is) then I really doubt it's them that's causing the problem. Are you sure it's not just an off-day and you weren't breathing in a calm manner instead?