Is it foolish to replace a mouthpiece for a borrowed horn?

[Charlatan]

Hello all! Just joined and loving the info here.

I've played a Conn 88H for years, mostly in community jazz bands. But it's recently gone to the shop for a few weeks. One of my band leaders kindly loaned me a Courtois 402T to use in the interim. He included two Yamaha Japan mouthpieces (marked as 45C2 and 45C2-12). I've been using the 45C2 and after a month of practicing I feel like I've finally gotten more or less acclimated to it.

My playing is decent with the horn/mouthpiece but I'm vaguely disaffected with it (when I look at it I think "wow, that's microscopic") and have been considering getting a new mouthpiece. My upper register is good but could be improved a little. The main goal is to improve my endurance while helping (or at least not hurting) my upper register.

Complicating things, I've started looking to buy a tenor trombone. Would like a Conn 6H/48H.

The question is thus:

Is it a bad idea to replace the mouthpiece on my loaner before purchasing a horn? Is the feel/fit of the mouthpiece going to be different enough (on a new horn) such that I should wait?

Thanks in advance.

[BGuttman]

I would buy myself a new mouthpiece. Leave the two Yamaha mouthpieces in the case with the loaner. When you are done, you now have a mouthpiece that will be good for another tenor.

[JohnL]

Buy something that fits your face. As long as it's not too far out of the mainstream, it'll probably be fine on any small bore tenor.

[Charlatan]

That's the kind of advice I was hoping to hear. I'm certainly not going to purchase anything out of the ordinary, so it seems like I can move ahead with the mouthpiece portion of my plan. Thanks again.