Stefan,
the original \hideCurvesFrom is here:
http://lsr.dsi.unimi.it/LSR/Snippet?id=613
If you're interested, you can look at the example section at the
bottom of that file. The numbers represent the padding around the
object. I think the units are staff-spaces. When all four
numbers are 0, the curves can touch the object but not go through
it. If all four numbers are 1, then there's a padding of 1
staff-space on all sides of the object:
#'(left . right) #'(bottom . top)
Different values work better in different situations.
Hope this helps.
- Mark