I will take a little space here to welcome jfoster to the board. j, I also have a nice Warmoth. Since you are not far( N.H. for you and Mass. for me), any time you are around, let me know. I have a nice Excel you can play  
 
 
Paul, The good one

Back to the original question of bone vs brass nut.  A bone nut is useful on fretless basses.  The idea is to have the tone of the fingered note and the open note to be as close as possible.  A brass nut on a fretless bass is certainly acceptable, but when an open note is played, the brass nut makes the note a bit more aggressive.

As far as the question of how the adjustable nut goes, I am going to give it a try.   There are three holes in the top of the nut that holds three allen screws.  The two on either end act as the height adjustments as the height adjustments on our basses bridges work.  The center allen screw is different.  It screws into the brass plate underneath the nut and locks it into place.  That is why it is important to unlock the nut with the center screw before making adjustments.  The outer two screws do not screw into the brass plate, but just push against it to raise and lower the nut.

Thanks Paul. Might just have to take you up on that some day.

Dela has it just about right - the only clarification is that the center anchor screw threads through the base plate into a small insert under the plate. The anchor screw is fully threaded with a socket cap, but from the top looks almost like the pivot points height screws without heads.  
 
Jfoster - you can order a nut blank from us that you can install on any bass, but mind you, it's not an entirely easy job and should be done by a good guitar repairperson. For a 4-string the nut blank is $45, and for reference we charge $75 to install one.

Thanks Mica: I know a few luthiers out here in NH who could install it for me. I would like to go ahead & order that. Can you send me the info on that?

Can you email me your mailing address jfoster? The form isn't in electronic format yet so I'll have to mail it to you the old-fashioned way.

Thanks Mica,that was fast. You can mail it to the following.
John Foster
C/O LaValley Building Supply Inc.
PO Box 267
Newport NH 03773
Thanks again :^)