I'm no expert but you can probably call the instrument that you're having made what you like, it won't hear you.
I agree
I have got a "hybrid" instrument that was made for me as follows, because this was the sound that I was looking for and I am used to playing ukuleles: baritone scale (21.75"), baritone neck width, wooden bodied resonator built for steel strings - although it also works very nicely with classical strings.
When I was using steel strings I got really sick of people telling me that it was not a Baritone Ukulele and that it was "really" a tenor guitar. The scale is a bit short for a Tenor Guitar, the neck definitely too wide and body size too small for a Tenor Guitar.
I told the maker that I was being pestered about what sort of instrument it was and asked him what he would call it. He thought about it and then said,
"A Squillum".
So now that is what I say it is. If anyone then replies,
"What are THEY?" I just say,
"There's only one, and this is it." Saves a whole lot of bother! If he ever made more of them, which is unlikely, I do hope that he would call them "
Squillums"!
Though it probably would not take long for someone to say,
"Actually, this is an Argentinian Bandersnatch. My grandfather had a photograph that he took in 1926 in Tierra del Fuego of an old man playing one of these and he said that the old man told him it was a Bandersnatch. I later discovered that it was built and designed by the Norwegian explorer Lars Andersnage and the Welsh-speaking locals called it, affectionately, Ap (son of) Andersnage. This was misheard by Spanish-speakers in the area as 'Bandersnatch'. The earliest written record of this instrument, on a Wanted Dead or Alive poster for notorious bank robber Hiram J. Squillum, describes Squillum brandishing his Bandersnatch at terrifed bank staff. IMHO this is how confusion about the name arose."
I have used both Tenor Guitar Strings and steel Guitar Strings on it in the past but I happen to have Thomastic flatwound classical strings on it at the moment. They look rather like steel Guitar Strings so, when the usual questions start, I think I might have to start explaining it as something like, "
A Baritone ukulele version of a Dobro but with classical guitar strings, like a little Del Vecchio Dinamico."
The original question is about maximum scale length for a Baritone but minimum length is also grey area, as has been mentioned. Some "ukulele sizes" seem to have got bigger over time, a bit like the way the newest model of car is always bigger than the previous incarnation, until eventually the manufacturer comes out with a new, smaller model and gives it a different name. (I have seen several descriptions of old Tenor Ukuleles that include a caveat along the lines of,
"this is more the size that would be called a concert ukulele today".)
My old Harmony baritone has a 18.75" scale and I have been told more than once that it is too small to be a Baritone and is
"really" a Tenor Ukulele. (Are tenor ukes getting bigger too??)
I agree with Dirk about tuning being a red herring. I have got a Soprano strung with Southcoast Ukes cuatro strings and tuned DGBE - it is still a soprano ukulele. (Personally, I would be more comfortable thinking of it as a tiny cuatro rather than a tiny Baritone. The form of the tuning seems more relevant than the sound that rings out when you strum open strings.)
I wonder . . . with there being more and more "non standard", mix-and-match combinations of scale length, body size and depth, with a whole variety of naming conventions, will there be more of a tendency to focus on the spec details, in order to work out what cases might fit and what strings to use for particular tunings? And use of equivalences, like,
"Brand X model Y is much the same size as Brand A model B"?
It is interesting what Dirk explained above about the naming/marketing history of the Pono Nui:
"The Pono Baritone Nui was originally called a Tenor Guitar (in one way or another, can't recall exactly). The body is as large as many Tenor Guitars, the scale length is the same. That body has a depth of resonance suitable for a C note, so it has the depth for a C g d' a' fifths tuning. The only reason it doesn't work as well as a traditional Tenor Guitar in that tuning is that the 1st string is delicate in steel. You'd replace it all the time with classical material.
They decided that since it was strung with classical strings, the name "Tenor Guitar" was confusing those who were used to a Tenor Guitar being strung with steel. So "Baritone Nui" was decided on as something that people might not get as confused about. I have no problems with a builder naming his instrument in whatever fashion he feels appropriate. And I have no problems with the name Baritone Nui. However "Nui" in Hawaiian signifies "Big". In effect, the name means "Big Baritone".
But based on significant increases in both body and scale, we'd say the Baritone Nui is not a Baritone Ukulele. The key is that it's a NUI. We use the term "Classical Tenor Guitar", but as I said, no problem with Baritone Nui; just remember the "Nui"."
Exercises in ukulele "instrument taxonomy", attempting to classify and categorise, are cross-cut with marketing strategies.
I have been looking at the Cordoba Mini recently - scale length 20" so falling into the "Baritone size" area. In discussions about the Mini there seems to be quite a difference depending on whether the comments are primarily from people who are first and foremost ukulele players or are from people who very obviously only have a guitar background.
"Ukulele players" seem to "get" the Cordoba Mini, understanding and welcoming it as a type of "guitarlele/guitalele/guilele etc." - and to a lesser extent as a "mini classical guitar" if you string it differently.
"Guitarists" often seem to be quite confused about it, because of the option of ADGCEA tuning and also because it is small but does not have steel strings, ie. like a Tenor Guitar or Parlour Guitar.
Cordoba seem to be targeting guitarists, by calling it a "Mini" (miniature guitar) but my impression is that they might have been better off targeting ukulele players and calling it something like a "wide necked Guitarlele". . . . or maybe not. Perhaps there are still so many more guitarists in the world than ukulele players that it makes way more sense to "sell" it as a miniature guitar? That does not stop retailers marketing it and ukulele players "adopting" it as a type of "Guitarlele", of course.
The Cordoba Mini also made me think about the disputed birth and subsequent history of the Baritone Ukulele. Whether or not the Baritone was first invented as a small, simplified guitar by Herk Favilla it is, at the moment, primarily thought of and marketed as the "big ukulele" that, perhaps, was instead envisioned by Arthur Godfrey and invented by Eddie Connors.
Give it another ten or twenty years and I bet the parameters and terminology of a discussion like this will have changed again
Best wishes,
Liz