@Booli I have the kala rounds on my hadean bass, they are nice. I'm not far away from you if you ever want to try them. I now have a kala 5 string and love the 23" scale. I'm waiting for their rounds to be available for that one, they said they're coming soon.
Thanks for the offer
, I'll send you a PM so we can discuss...
Having recently discovered fifths-tuning over this past weekend, I'm also kind of thinking about stringing my solid-body Hadean like a mandocello, in fifths, GDAE, G1-D2-A2-E3, using some D'Addario XL Chromes flatwounds purchased as singles to get a custom set with the proper tension, using their string tension calculator to figure it all out - stringtensionpro.com.
I have the D'Addario chrome flatwounds on both electric guitars and on my DIY 25.5" scale piccolo bass which I converted from a 6-string strat copy to a 4-string instrument. I was using it for a while as an octave baritone uke and had it strung with the La Bella nylon tapewound strings. Intonation was way off, no matter how I adjusted the instrument or used different strings for different tensions at pitch. I think that the folks that control the QC at La Bella are out to lunch. I read many reports online from other folks with the same problem, sadly it was after the fact. I'll do more homework for next time.
I also have an unfretted strat-style neck, which easily fits the neck pocket of the Hadean solid-body uke bass, and I was considering swapping this neck with the one on it now, and see about learning to play it fretless. It fits nicely, but extends the scale length to 22.5" which I figure is a good thing, since longer scale will make intonation easier on a fretless, as opposed to a shorter scale...but I need to carve out a weekend or two to first fill the tuner holes with dowels, and then drill 4 new holes that are 35/64" in diameter to fit the u-bass tuners I got from largesound.com for $32 per set. Using these tuners will also let me use the poly rubber strings as well as others instead of using standard bass tuners and then trying to file the slots wider - tried that, broke a tuner and got the obligatory gash into my palm as a battle scar...
With the fretless neck, the saddle can stay in place since I am not trying to match a specific fret scale. I figured that I'd use a strobe tuner app to find and mark the side dots for the finger positions and just leave the face of the fretboard unmarked, but protected with 10 coats of polyurethane spray finish so whatever strings I use dont chew up the fretboard over time.