Cutting a Eb Tuba

[The Big Ben]

A repair person could unstick the slide with a minimum of effort. The 'flatness" could be solved by the right repair person also. If the horn is really beat up, it could have some leaks in it that would cause intonation to go all higgledy-piggledy.

If you say where you are, maybe someone could suggest someone who could help you.

[tubaforce]

Hi! Tell us where you are, and we'll come up with recommendations! You don't want to let just anyone hack on your horn! Al.

[BlueGrassBrass]

It could have leaks like said above, as well as if there are some major, (or not not so major) dents in the horn, it could be causing this as well. Also, if your spit valve corks are old, I can almost guarantee that are not sealing properly, thus causing a leak. The mouthpiece may also be a culprit as you have already stated. I would look into all of these issues before cutting. That is an abolute last ditch effort for an intact vintage horn.