I see that you have it solved already, just wanted to add that if you want something more advanced then it's often quite easy to use a
, see http://dev.w3.org/SVG/profiles/1.1F2/test/svg/masking-path-11-b.svg for example.
However, if you can avoid masking and clipping (e.g by just drawing things on top) that usually leads to better performance/user-experience.