Volta brackets and chaord symbols

[Thomas Scharkowski]

Hello list,

I have a chord symbol above the first note in a volta bracket. 
This chord symbol collides with the bracket. Is it possible to move a 
single chord symbol?
Changing the bracket height with 
"\override Score.VoltaBracket #'minimum-space = #3" does not help, 
the number still meets the bracket.
The other way around "\set Staff.minimumVerticalExtent = #'(-5. 9)" 
does work, but the symbols are too far from the staff now.
Is there a way to place the chord symbols under the bracket?

Thank you,

Thomas
2.2.2
cygwin