I think I have the answer.

My aperture needs to be smaller on the shallower mouthpiece and tongue arch does not need to be deployed as soon. I taught science before retiring, I think I was not getting a laminar flow. Non-laminar flow is characterized by turbulence instead of a smooth flow where all the fluid is moving all in the same direction. This may have resulted in constantly changing the lips’ vibrations, and impeding vibrations. In a sense, it may have been like overblowing.

Then again, I may not know what I am talking about.

I think I will just stick with the 3C. I am just playing for fun and have no performances.