The market for a 3/4 tuba definitely is small but they can be used in a lot of situations. If I had one, I would use it for pit orchestra, remote recording, brass quintet, and big band. A contrabass tuba with a small .689 bore can work nicely as a bass tuba replacement when you have a gig with both low and high playing. You get the ease of playing a smaller bore but the low range stability and fingering simplicity from the longer bugle. As an aside, I have had my 6/4 CC tuba since I was 14 and sometimes it feels like I am driving a F-350 to get groceries when you just need a Honda Civic. Now that I have access to a 4/4 CC tuba, I don't take my 6/4 out as much. I can't justify the cost but I would love to have a 3/4 CC like a Rudy Meinl as well.
As a tuba player for many years , Kanstul made this tuba 3/4 size was for doubling bass trombone and tuba and also for playing small groups as a quintet, trios ,and solo work
I have the same problem with the valves on my Kanstul 200/4 convertible tuba. I found that if you take your thumb and rest it on the first tube from the valves (that's between you and the valves), it can allow your hand to make a C shape and you can press that 4th valve quicker and easier. If that doesn't work, use the "trumpet method" of resting your thumb between the 1st and 2nd valve, near where they connect
I just recently bought a really old hawkes and son Eb tube that’s in pretty decrepit condition but i find the ergonomics are really nice. it’s unfortunately missing a slide for the forth valve though
