Well let's give it another try.
bssist,
sorry, no experience w/ the soundcomposites fb's, or any carbon fibre fb on a DB. But they do seem interesting.
Some 20 years ago I made fb for a fretless 5-str BG from carbon fibre (using only full-length strands lengthwise, with epoxy, and compressed into a polyester -'ve mold during setting. First made a softwood painted/polished fb to make the mold, and of course used a first epoxy layer, later to serve as top coat.) It's quite a rounded fb (not as much as on a db, but more than any bg I've ever seen), and I find it the sweetest fb I've ever had on a bg. In a spotlight it looks beautiful too, showing the lengthwise strands - but in normal light you don't see much of that. Good sustain & growl, stable under long-term stress, and long-lasting too (no work required yet), using D'Addario chromes, which have a finish similar to db steel strings (so not roundwounds). So I feel that carbonfibre has potential to make a good fb, also for a db. For planing, which will be required eventually, suggest to do it timely, and first to re-coat w/ epoxy, so that you don't actually grind into the carbon fibre.
On other ebony alternatives: on my latest db, I tried garapa, that's another (cheap, reddish) south-american decking wood. In order to reduce the weight of the instrument I wanted to try a lighter wood (SG ipé = 1050 kg/m3, SG garapa = 825 kg/m3), yet still hard & stiff (E ipé = 15.2 kN/mm2, E garapa = 16.8 kN/mm2, in the grain direction). It should be withstanding string tension fine, but the Janka hardness perpendicular to the grain is a bit lower than of ipé (ipé = 11610 N, garapa = 8250 N). But of course that is no indication of how rapid it will wear. The downside of garapa is that it is a bit courser grained. Sofar its performing fine, but I've only used it for a couple of weeks.