Relative thickness of PianoStaff Braces

[Jonathan Wilkes]

Hello,
     I'm having trouble tweaking the Brace at the beginning of a system. 
My test code is below; basically, I'd like to make the brace oonnecting 
three staves less thick.

That brings me to my second question.  I've attached two pngs, one of 
Lilypond braces and the other from a Durand score of Debussy's 1st 
Prelude, Bk. II, available here:

http://imslp.info/files/imglnks/usimg/d/dd/IMSLP00510-Debussy_-_Preludes__Book_2.pdf

Both Durand braces are of course much thicker, but the point is that they 
have comparable weights (not sure what to call it).

Lilypond's large brace basically looks like the smaller brace has been 
enlarged by about 170%, which looks a lot less elegant.  Shouldn't the 
brace be stretched vertically without changing the thickness?

-Jonathan

example code:

\version "2.12.2"

\score {
        \new PianoStaff 
%         \override PianoStaff.SystemStartBrace #'thickness = #0.2
          <<
          \new Staff = "rh" {
          <<  { c' d' e' f' }
            \new Staff \with { alignAboveContext = "rh" } { c' d' e' f' }
          >>
          \break
          c' d' e' f'
          }
          \new Staff {
          c' d' e' f'
          c' d' e' f'
          }
        >>
}

\paper {
        indent = 0
}

%\layout {
%       \context { \PianoStaff
%               \override SystemStartBrace #'thickness = #0.2
%       }
%}

durand.PNG
Description: PNG image

lilypond.PNG
Description: PNG image