And what are the parameters for mouth size: jaw, or lips? Do you factor in tongue size? Do you do the volume of the inside of the mouth? And once we pick which of these to measure, how do we determine what is normal vs. large or small?
And then, how do we determine the effectiveness of fellatio? You can't really go by completion, because that's pretty much guaranteed, barring TMJ issues for the blower or sensitivity issues for the blowee. You can't necessarily go by speed, because there are many other variables that determine this.
even passive variables like lip fullness and current moisture levels of the mouth are crucial to the success or relative failure of a hummer
this is going to be the best grant request ever written