Scaling accordion register symbols

[Karol Majewski]

Hi,

Recently I'm experimenting with accordion register sets. I've looked into:

http://lilypond.org/doc/v2.17/Documentation/notation/accordion
http://lists.gnu.org/archive/html/lilypond-devel/2011-07/msg00250.html

and found that those symbols cannot be scaled properly when using:

\new Staff \with {
  fontSize = #-3
  \override StaffSymbol #'staff-space = #(magstep -3)
}

I mean... the symbols are scaled properly, but the distances between the dots 
are not.

How can I improve the code to make it work?