I’m someone who recently has rented out a tenor trombone for orchestra use but is a bass trombone and euphonium primary (Douglass Yeo/Schilke 60 on Bass and SM3XR on Euph) and am having trouble finding a mouthpiece which can be useful for tenor but not kill my chops. The tenor I am renting is a Conn 88HO.

If you are using a SM3 on Euph, try a 3AL. About the same rim diameter as the SM3 but shallower.

Doug Elliott XT106N/G/G8 or G9

I use a Greg Black 3G/5G.

Doug Elliott can put together a great set up for you, give him a call

Try a 3G / 3AL size as that is similar to your euph mouthpiece. Or go 1 size smaller to a 4ish!

Or just use the bass bone or euph mouthpiece in the tenor. I wouldn't recommend it for playing 1st tho.

Or approach it as a completely different horn and use a 5ish. Would make it easier to cover 1st if asked!

All 3 methods have pros & cons, just find what works for you.

Depending on how much effort I thought it was prudent to put into switching, I might consider an Elliott LB114 rim on a shallower tenor cup like an LBG with a G8 shank.

I've been going through a similar journey lately. Primarily play bass trombone, but an amazing group has a tenor opening and I'm getting my tenor chops in shape to audition. I hate my tenor mouthpiece but have never had the motivation to find something better, as I hardly played it until recently. Large Shank tenor btw.

There are so many designer/artist MP options out there these days. And they are PRICEY. Its hard to justify experimenting with them. Even standard ones have gotten so expensive. So I've been borrowing mouthpieces from other guys I play with to see what works and doesn't before spending much money.

This is my own experience, but may help you plan a similar path. For each of these I took a full day or two to play exclusively and adjust to as best as possible.

51C4L - Starting MP. Sounds very constrained and is easy to overblow. The high range is effortless though.

Yamaha 59 - My bass MP. In the ballpark of a 1 1/4G or Shilke 58. The overall sound is great (I may be biased) but a bit too much like a bass bone for obvious reasons. The high range is definitely not there for what I need on Tenor.

Wick 4AL - Sound is much better than what I started on, but did not like the flat wide rim.

Lindberg CL2/CL4 - The crazy bore didn't bother me but these seemed too shallow and the rims were a little small. Really just tried these because someone had them and suggested it.

2G - This is an oddball mouthpiece, squarely in between traditional tenor and bass sizes. And that's what it was for me. Sounded mostly like I wanted for a majority of the range, but the high range was not there. Might work for playing 2nd bone, but one of the audition pieces I'm working on goes up to a C multiple times and it was harder to hit the C on this than my 59.

4G - Current front runner. Sound is close to what I want. High range is there. The sound will probably improve as I grow into it more.

3G - Waiting to get one from a friend. But am expecting it to be a little too big. Might also be a contender for 2nd bone playing.

After playing bass trombone for more than a decade I was asked to play a gig on tenor. I used a Bach 3G, but it didn't feel that comfortable. I tried a number of Greg Black, Doug Elliott, and Laskey mouthpieces. Ultimately I landed on a Doug Elliott combination with a lexan rim. In general, I like mouthpieces with a larger rim diameter, narrow rim, and shallow-ish cups. Doug's system makes it easy to dial in a good mouthpiece setup. I have said it before and I'll say it again, lexan rims are so comfortable.

I have had good results in all registers...also excellent for a one trombone book for B'dway!

.547" Bb/F Bach Soloist with a Melton 4G euphonium mouthpiece (made by Meinl-Weston).

I have not been able to obtain specs on the Melton, but consensus seems to be: "a la Bach 4G".

If you have the money and the time, dial in something with Doug or look into a GB setup. If not, you already play a 3 rim, find something around that’s a little shallower, use the rim diameter, sounds like you like Schilke, maybe give one of their’s a try, otherwise, 3G or 3AL.

I use a Doug Elliott set-up for large tenor: LB114, I cup, I8

I also find that I like the lexan rim for tenor, though I don't use one for bass unless I'm playing in cold weather outdoors.

Doing same as Original Post described.

Was playing a Schilke 60. Consulting with Doug got me to a LE MW 113 RIM, L8 L-star CUP, L9 SHANK for bass. Liked it so much I went back for a consult on my Bach 42 and found the XT N 103 RIM, XT G-star cup, with a G 8-star shank was a great fit for me over the Wick I had been playing.

The modularity lets you try different combo's (Doug sends a selection of what he thinks will be close - return what you don't need). Definitely worth doing a consult with him.