Adjustment to tablature output

[Christopher Webster]

Is there a recommended way of adjusting TabStaff output so that 
the note-heads (fret indications) appear _above_ rather than _on_ 
the lines representing the strings, please?  This would make it 
more closely resemble English renaissance lute tablature, and I 
have a particular piece of transcription for which that is a 
desirable goal.

I've got as far as guessing that assigning a non-standard 
procedure value as the tabStaffLineLayoutFunction property of 
Tab_note_heads_engraver would probably get me towards where I 
want to be, but alas I'm too stupid and/or too ill-informed to 
see how to write such a procedure.

Thanks in advance for any help or advice.

            Christopher W.

Sweden.