First, I want you to look really really hard at this picture. See if you can figure out what it's all about.
I never really had any formal instruction when I was young. It wasn't until I was 40 years old, after trying to pick up the horn again, when I sought instruction. A local dude, Mr "Lawler Bb" on this forum, did his best with a difficult student.
So much of what I read on here was, if you can't play a middle of the road mouthpiece, then there is clearly something wrong with you. I tried and tried and tried with normal mouthpieces, including the perfectly-fine Schilke 14, some others in between, a custom set of pieces made by Doug Meeuwsen, a custom set of pieces made by Mark Curry, and the latest old-but-new pieces offered by Steve Cass.
After half a decade, none of it worked for me. I struggled to get A above the staff or play more than an hour. Everything I read on here said it was clearly my fault... I wasn't practicing right. I wasn't practicing enough. I was practicing the wrong thing. My horns were the problem.
None of it was true.
In desperation, I grabbed one of those pieces, a Buescher Duo-Cup 88-E. They're not all the same. Variation is the name of the game. But I had three of them with the same characteristics. Small diameter cup at .630 inch. Throat around 27ish. Moderately tight backbore.
Sharp as all get out bite, and flattish rim.
According to most people on here? Unplayable. Too extreme. Buy a 5C and just practice. If it feels better? HAH! Honeymoon! Just wait a couple weeks, you'll suck just as much as you ever have.
All you classless morons can just shut it.
Not only did my endurance double, so did my range. Where before I only had shame in the community band, I was able to finish a 2-hour rehearsal. Where before I could maybe play an A above the staff, I was cracking off high C, D, E for grins on the last note of a piece.
I've been playing this piece (my "backup" while Charlie Melk has the primary one gold plated) for a couple months now. I think the honeymoon is over.
My purpose in this message is only partially genital waving. The other is... when conventional wisdom tells you something and it doesn't work... try something different! If you're struggling and feeling pain and heartbreak because you can't do what these others say you should do, easily... try something else!
I've met some nice people on this board, some in real life, and some virtually. But it does amuse me when people who have been in the industry for decades tell me to ignore the advice I see, I'm doing fine finding my own way.
You should find your own way too.