Trombone doesn't "fit" anymore

[Dsalad]

I am returning after 40 years and about 60 pounds. I'm finding my neck is kinda pushing the mouthpiece a little cockeyed on my lips. I play a King 3B(f) from 1980ish. I would love to get a new (larger bore) horn after I get my chops back, I played a 42G (rose gold bell?) in college. Do larger bore horns or more modern horns have more "neck room" for less than petite people like me?

[BGuttman]

Yes, larger bore horns have a wider "reach" than your 3BF.

As someone familiar with your problem, I also found that opening the dihedral angle (between the plane of the bell section and the plane of the slide section) can also help with the fit.

[AndrewMeronek]

Yes, that is definitely a thing. The distance between tubes in the handslide is a bit wider on "large" horns. I don't have any idea why this is a convention.

I have always had a larger than average size neck, and I had a "small bore" slide custom-built with a wider crook (so the tubes can be mounted wider apart) and that was a noticeable improvement for me. Other people have tried using a mouthpiece with a "bent" receiver with success too. I actually like how the change in crook makes the horn blow, so for me that is a better solution.

[AtomicClock]

There is a nice survey of slide widths in this other thread:
viewtopic.php?t=18492

[JeffBone44]

Wycliffe Gordon is a big guy. Look at how he gets his trombone to fit.