In beat-up condition (out of the shipping box, NO repairs, WRONG felts) I played an orchestra-sponsored quintet rehearsal and outdoor quintet concert with it, and it was enjoyable (for me) and wasn't difficult (even with only three buttons from which to choose to mash) to place pitches where they needed to be (close to right, and quite flexible, without the resonance suffering while taking advantage of the instrument's offered flexibility...Well...C/B and F/E (1-3 , 1-2-3) required more convincing that some other pitches, but whatever...
The question will be: "whether or not to rig it up with a fifth rotor".
The (will disappear) top-action valveset is .665" (nearly 17mm - a sort of odd-sized, but descending from an outside slide tubing OD of .750", thus understandable as to how it came to be) bore.
I've located a "sparkly" condition 2341 front-action valveset for it.

(...and - these days - with Anderson not doing popular-priced valve rebuilds, replacement valvesets had d@mn well better be "sparkly".)
Of course, that King 4-valve valveset is .687" bore...roughly 3% larger than the Holton valveset...
The mouthpipe tube (though patched: apparently original) seems to be a bit on the large side (at least for my proportional/resistance tastes)...so - if a subtle amount of resistance is lost in a 3% larger bore (??), it could (??) be recovered in the smaller mouthpipe tube which I'm likely to fabricate to my personal tastes...
...the premise being that: Resistance is thought to be a player's friend, when it comes to playing false tones.
The thing is this:
The false tones are EASY - NEARLY "Conn sousaphone easy", and easy-to-play-in-tune...BUT (well...) neither loud nor any way to make them "growl" (if called for), which would be possible, if playing them on the 2nd partial (ie. with a 5th rotor).
A 5th valve would take TIME to design/install, but would NOT be "difficult" - as the thing seems fairly wide-open, and with a L-O-N-G-@$$ main slide.
This might be a "casual-play" instrument, but PROBABLY NOT for playing in jazz bands...probably not ever...and VERY FEW things that I play are "casual". I don't paint/represent/consider-myself-to-be an "artiste", but I typically only show up for remuneration, and am d@mn-well worth remunerating...

...so (with this info supplied) 5th valve or no...OR, maybe...
...go ahead, slick it out, build it, but put NO FINISH on it, play it here/there/yon, and decide on a 5th valve later...??

bloke "If this tuba turns out as I expect it to, OTHER THAN MY SOUSAPHONE it will be the FIRST "considered-to-be-one-of-my-personal-take-to-gigs-instruments" B-flat tuba I will have ever owned.
