John:

If I might clarify a bit:

The aperture is the opening created by the airstream, not by opening your lips more, imo....

I think, perhaps, that it's important to clarify the differences between lip compression(flexing of the orbicularis oris, or *centering-in*) versus lip roll(flexing of the levator and mentalis muscles, which control the degree of outward or inward rolling of the *red* or membrance of the lip tissue)....

The biggest difference I notice in my own playing is that playing on a smaller mouthpiece requires more inward rolling of the membrane(to keep the rim in the *white* or muscle of the lip), whereas the use of a wider cup, or a deeper one allows me to use more outward roll of the mpc, thus enabling a darker sound....

The use of a *wider aperture* on a smaller mpc can often create the *bottoming out* sensation, just as the use of a highly rolled-in embouchure on a deeper cup can cause faster fatigue....

Imho, it's best to be as versatile as possible and learn to use both large diameter and small diameter cups, as well as both deep and shallow cups....

I'm interested to hear everyone's views on rim thickness and shape, too...

Good thread!

Best,
Jeanne