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I ordered a new nickel-silver leadpipe from Cerveny for my 1980s Piggy. I received it today, and it looks to be pretty close to the one I'd like to replace. Shape is almost identical so I think it will fit, and I measured with calipers throughout the length of the tubing and the taper seems to be pretty much the same, with the exception that the large end of the new pipe measures about 21.6mm for the outer diameter and the large end of the old pipe measures about 22mm.

Four tenths of a millimeter difference between old and new -- too much play there? I'm worried about the new pipe being too small and not fitting the ferrule connecting to the valveset.

For a nice tuba that I really don't want to screw up, I will probably take it somewhere to have it installed regardless, but I wonder if I should see if I can get a replacement with a slightly larger large end. Or can/should the end of the ferrule be shrunk by 0.4mm?

If I had one, this would be a great excuse to add a fifth valve, so maybe I will hold off on installing the pipe until I have a good candidate lined up.

I say it should be fine. The story I told you before about a new pipe messing up my 601 was way more different than that one, and the difference was much earlier in the taper

That's only 15/1000ths of an inch.

Most of the tubas of that model have a ton of straight mouth pipe heading into the first valve, so why don't you just stick your steel tapered rod in there that's in that size range and tap on it with a dent hammer until you've picked up that taper and work the mouth pipe down to the 22mm mark on your tapered rod? If you don't like the hammer marks, sand them out.
At the very least, I would recommend that you do the hillbilly thing and pound of 22mm dent ball into the very end of it, which will give you a little better chance of not putting solder inside the joint where you don't want it...
You know: those hotsy-totsy repairman (who double as acousticians) always telling us that we don't want that to happen.

Terrific that you were able order it and it came in pretty much as expected. That’s a big change from recent history. Pretty cool!

Thanks. Have not ever really worked with nickel-silver before so I wasn't sure how well it would react to that much expansion. This gives me more confidence.

@MiBrassFS, yes, it was actually quite easy. I reached out to Buckeye Brass and Lonny hooked me up with the part. It took about 6 weeks to arrive, in great shape. Price was very reasonable. I'll post a pic or two.

I don't know about annealing and jamming it up on a tapered rod several times, as I haven't had as much success annealing nickel brass as I have regular brass. It might be worth a try, and you could avoid hammer marks if it works.
If you have some .005" gradation dent balls way up in that range, you could pound them in there and then - if you have a dent machine - you can iron out the swells at the ends of each of their ranges.