Hello
the material that I used is as ferrite beads is this
http://www.ebay.it/itm/140493166602?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649I stacked three with a drop of glue and the poles (that are actually alnico, not steel) pass through. They are adjustable, however not through the screws that are dummy. If I want to raise a pole I use a magnet to pull it out, or I can push it to make it lower.
I decided to use the ferrite beads because I have no tools to drill properly laminations, and thinking that this would add some inductive material with very little eddy currents. The principle is the same as using laminations.
I am now working to an alternative design where laminations are aside of the poles and will install on a Tractor bass clone that I am building.
Regarding how the pickup sounds I cannot compare to the real thing, since I have never played, but listening to the samples on the Dark Star site, and comparing to what I play I can recognize some similarities.
Neodymium is very good to my ears. I have winded until now 4 Jazz pick-ups, 1 split coil precision-like and two humbuckers (actually 3 but one was crap due to constructive defects). For all I used steel poles.
