Another one of those mouthpiece questions.

[Mark]

Considering that I'm quite a young player. I was told both the PT88 and the PT88+ would suit me fine

Do you mind telling us who told you that the PT88s would be fine?

[geneman06]

Both the 88 and 88+ are very large mouthpieces, they both produce a big dark sound and are great for playing in the lower register. I suggest you try as many mouthpieces as you can, there's a lot different ones out there. Consider what you're looking for; rim characteristics, bowl shape, bowl depth, metal it's made out of. also consider what kind of playing you do most, and pick something thats fulfills those needs.

[josh wagner]

Maybe try out a PT-48+ or just a PT48 thats what i used to play on it has about the same feel as a helleberg sorta but it's nice and not as huge as the PT-88s, just a suggestion.

[iiipopes]

Ha! After (mumble) years, my corners still give out occasionally after a demanding rehearsal or performance.

But they're all correct.

If you like the shape of a Bach 18 cup, you could try an LOUD LM-7, or if you want to go really deep, a Wick 1L. And there are dozens more. Here's a good chart for some ideas that might be able to help you figure out the direction you want to go. Of course, this is just raw cup diameter, and says nothing about depth, rim, throat & backbore, etc. Also remember that Bach cup diameters are notorious for being larger than spec in real life; I have one that is a full 1.28 cup diameter rather than the "spec" 1.26:

http://www.ibowtie.com/tubampccharts.html

But first, as stated above, get your corners firmed up over the next few months and make sure you have reached the limit with your 18 before you change mouthpieces, because things could get worse instead of better. At some point, everyone has a limitation of just how much muscle is there in the embouchure, and if you exceed that with the cup diameter, you won't be able to "fill it up," and you will actually lose tone, flexibility, range, etc.