As a double bass player, I,ve tried to find an instrument, which could coexist with upright and create new sound possibilities. I've chosen 5-string version and put high C instead low B. All solo parts, improvisations (arco and pizzicato) in high register sound fantastic - much better than I expected. Bass is well-made, solid, tuneful and playable. I could recommend it for everyone, who likes all "hybrid" options. One can easy operate along whole fingerboard (soft and silky smooth) and construct complex chords with harmonics and open strings (great, looong sustain). But - definitely - this smart and nice instrument can't replace upright bass. No solid punch, deep response and specific, acoustic tension. It was not made for it, but - somehow - few of bassist try to use it as a "second" upright. Not my way.
Apples and oranges :-)
I replaced original strings with Flexocores and high c Thomastik, and it works well.