DP wrote:Gosh a 4 valve f is fine for Tuba 2 or "even" Tuba 3 in most decently-voiced quartet arrangements
and quite use-able for high parts in larger ensembles (Berlioz

)
It used to be that people looked to replacing their equipment when what they had was limiting their playing.
Now it seems the common advice is to get the most versatile, flexible, feature-laden horn you can find
just in case you "need" those capabilities somewhere down the line.
As I said in my post, based on actual experience with a four-valve F tuba, I ran into limitations in about a year. And I was a second-rate amateur. Very few second-rate amateurs have access to situations where they can play Berlioz outside the practice room, but they are likely to want to use the instrument for quintet and other chamber music. I found the 4-valve instrument grossly limiting for quintet--some of the lit is voiced for bass tuba and some of it for contrabass tuba. If you want the lighter sound of an F for the former and you don't want to have to bring along another tuba for the latter, then five valves will make your life much easier. Certainly a 5-valve F tuba, for a person who actually wants an F tuba, would be at least as reasonable as a very small C tuba, which would have to be an additional instrument for most folks.
I've played a lot of tuba quartets, at all levels. And the third part (first tuba in an EETT quartet, which is by far the most common arrangement) often goes down low enough so that four valves would present some significant challenges.
So, the question is this: Should we advise an amateur to play a versatile instrument with the one extra valve, and play in the low register in the near term with the hope of decent intonation, or spend a decade learning the special fight required to play a 4-valve F tuba in the low register without skipping the bad notes?
It's not like your average 5-valve F is all that rare or expensive. In fact, I bet it's easier to find than a 4-valve F, at least anywhere English is the native tongue.
Of course, the agenda of the OP was hidden at first--he wants to cut an Eb tuba and adding the 5th valve makes that much more challenging, whereas I've written in my prior post and above applies to someone considering a 4-valve F versus a 5-valve F bought afresh. True enough--adding the fifth valve to a project makes it more challenging. Having done a similar project (without the fifth valve), I can say with some confidence that the lack of a 5th valve might be the least limitation on such an instrument, but maybe past performance is no guarantee of future results. My own project ended with an instrument that played reasonably well in and above the staff, and with a nice sound. But the scale below the staff was a whole other thing.
But for TubaChristmas only? That's where a 4-valve F might actually be at least a possibility--the first tuba part sits high, and the size of the ensemble will allow one to skip the notes that don't work, just like the guy does around here who shows up with a Civil-War-era over-the-shoulder Eb bass saxhorn (with three valves).
Rick "who hasn't met many ancient pea-shooter bass tubas with good false tones" Denney