To the Trumpet players out there...

[shawger]

A forewarning, I play horn

You must position the mouthpiece approximately "1/3 ON THE TOP LIP AND 2/3 ON THE BOTTOM LIP"

From what I've heard (and I've read the Arban's book), a trumpet embouchure should generally be 1/2 upper lip and 1/2 bottom lip. Horn is generally 2/3 top lip and 1/3 bottom lip.

Unless there is something dramatically wrong with your embouchure, it is generally not a good idea to change it. Changing your embouchure is a very long and difficult process, and unless the change is warrented, not much good will come out of it.

I am wary of people using equipment to even out the inadequacies is their brass playing. Before you start experimenting with mouthpieces and trumpets, try to find out exactly what is wrong with your high range. My guess is that you are increasing tension too much and not using enough air, thus cutting down on your endurance and high range. Brass instruments run on air. Inadequate air means that something will not work properly.