Cool! I can't recall seeing any 4 string Dingwalls here on TB. Love to try one!
I am sorry to chime in, this late. Most of the fanned fret basses I own are Dingwalls so my fanned fret experience is a bit "limited"


here are couple of 4str Dingwalls that I own
IMHO and IME the fanned fret is an advanced step in bass design
Many drummers that I play with, as well as sound engineers (when I go to record), ask me to bring the "fanned fret bass".
Ergonomics, playability, and most important tone, is what has made me choose Dingwalls as my main weapons of choice. My herd includes many high-end/boutique basses and competition is stiff.
The design allows for superb ergonomics and playability (balanced string tension is an added bonus, not only to the player but to the sound of the basses too). As far as tone goes, I am fortunate enough to own several samples (nearly 30), so I think I'm allowed to have an informed opinion. The quality of the components and assembly is consistent and top notch. As far as tone goes, it all depends on the bass I choose to use. My AB I sounds different from my "Uber Alles" Prima, which sounds different from my avatar Z1, which sounds different from my Villex-loaded Voodoo or my "Emerald Green".
I choose the one that fits and feels right for the project. Upper register chordal and tapping stuff are very easy for me on my Dingwalls. Some complicated stuff can be easily performed on a Dingwall.
I can understand that the concept may not be for all, but the overall result has to be heard and felt before rejected (you cannot describe taste; you need to taste it yourself)
As far as live tone goes, if you choose the right one you can make one big difference (that goes for any bass, as well as fanned fret ones). I've had friends who heard over the phone a Dingwall and another (similar in woods and electronics but non-fanned) very high-end/boutique bass and they could tell them apart
My 0.02