number of staff lines

[Nils]

Hello,

I would like to ask for a quick confirmation, since I never worked with an 
even-numbered staff line count.

If you reduce your stafflines with 
\override StaffSymbol #'line-count = #3 
or #1 or any odd number there is no question. With a treble clef the b' is on 
the middle line and lines are removed/added above and below.

with even numbers like #2 or #4 the b' is not on a line anymore but all 
stafflines move one step down so a' and c'' are now on the lines.

Is this correct and common engraver practice?

Nils