I believe that far too many trumpet players use mouthpieces that are basically too big. IMHO, going larger than a Bach 3C or the Yamaha/Schilke equivalent 14c4 or smaller than a Bach 7C or Yamaha/Schilke 11 should be considered 'specialized' equipment.
We seem to have no shortage of trumpet players out there who would say that very small mouthpieces are considered 'cheaters'. Have you ever seen a Bill Chase mouthpiece? It is about as small as you can possibly get and it served him very well for the type of playing he did. Could he have done that on a larger mouthpiece? Of course, but specialized lead players are artists in their own right. Those who do it for a living are very cognizant of what they are hired to do in the most efficient manner possible so that they can continue to do it for as long possible!
True lead players are also extremely rare. Think about how many people in your own community would be considered monster lead players...specifically the so-called 'screech' players. You would probably come up with a relatively small number in any given city. I can also virtually guarantee you that those individuals play on more 'specialized' equipment that probably falls out of a standard industry medium. In my opinion, you should only mess around with their type of equipment if you were interested in the type of air velocity that they themselves use for their specific job. Remember though that everything comes with a price. Extremely small, shallow mouthpieces simply do not resonate that well in a section. They may have good 'cutting' projection but try playing softly with a good attack...very risky. Of course, if you never have to play softly with a good sound then you should consider yourself a true specialist...go for it!
By the same token, the great orchestral players use equipment that would hover around a Bach 1 1/2 or 1C or the Yamaha/Schilke equivalent 16-18C4. These individuals should also be considered 'specialists' because they are. Playing in an orchestra requires the ability to blend first and foremost and occasionally lead the entire brass section. But even then, the best players are simply riding on top of overtones being laid down by the rest of the section. They are not trying to 'cut' through in the way that commercial trumpet players might want to sizzle over a big band or rock group.
I just finished playing with the Summit Brass this week. Allen Vizzutti, Allan Dean and David Hickman were also in the trumpet section. Playing with them was AMAZINGLY easy because everyone blended and played in tune and everyone occasionally had the opportunity to lead the section and lay down a style that the others would follow. When the section is in tune and balanced, it is very simple to play for long periods of time without feeling true fatigue.
It is my understanding that the great Bud Herseth began his career on something like a Bach 7C and only switched to a larger mouthpiece (Bach 1X...made for him) after his car accident so that there was greater sensation in his nerve-damaged lips. Obviously, Bud Herseth is one of the greatest orchestral players ever but his own switch to a large mouthpiece (largest ever at the time) was based on an extreme situation for a highly specialized job. However, since most classical players wanted to sound like him, many made the same switch without thinking of the potential ramifications. Specifically, working too hard to find the sweet spot...more on that later. Bud Herseth is one the most efficient players of all time and he was efficient on a Bach 7C for a long period.
Thus, the point of my ramble (I think I'm jet-lagged). EFFICIENCY!!! After starting on a Bach 7C like many of you out there, I graduated to bigger equipment...all the way to a Bach 1 1/4, 24 throat, Schmidt backbore. I love stats...it clears the room of everyone except trumpet players. So, now that we are alone, I can tell you about my realization. Unless I wanted to be Bill Chase, there was little point in playing through a pin hole. By the same token, it also seemed reasonably logical that unless I was recovering from nerve damage and needed to feel more of my lips so that I could play for Fritz Reiner in Chicago, I probably wouldn't need a 1X either.
Allen Vizzutti and I have discussed this often over the years and the simple fact is this, in order to play efficiently you must be in the sweet spot of a mouthpiece. A large mouthpiece has a bigger sweet spot and, as with oversized tennis racquets and golf clubs, it helps compensate for our very human ability to miss the centre of the note more often than not. To accomplish the same goal on a smaller mouthpiece you MUST be more efficient or it will back up on you. I describe backing up as basically trying to overpower the sweet spot.
Currently, I am playing a GR Mouthpiece which Gary Radtke made especially for me. This will be available very soon (complete with my website on it...the benefits of customization!). For years before that, my own equipment was made for me by a mouthpiece maker in Japan who worked for Yamaha. I don't know the exact dimensions but they are somewhere between a Bach 5-7 C or a Yamaha/Schilke 11. Never measured the throat or the backbore and I didn't really care because it basically got me to where I needed to be. I could pretty much do everything I needed to do in any register I needed to play in with that mouthpiece. Could it have been a more perfect mouthpiece? Of course! Will I obsess about trying to find an elusive solution? Of course not! The answer is fluid anyway due to the fact that my body, lips, dental structure, and vital capacity will always be changing naturally due to the aging process that everyone of us is undergoing as I write this. Now, if your thing happens to be the quest for the perfect mouthpiece, then at least be honest with yourself, it is the chase that you are into and not the solution.
The bottom line is this (again, IMHO) the name of the game is efficiency and flexibility and the best solution for an all-around game is middle of the road equipment coupled with focused, intelligent practise. Have fun experimenting but don't let it be the answer to your problems!