HoWTo Remove FacesMessages from JSF2FacesContext

Hi.
We use SWF and JSF 2.
I need to remove some FacesMassages from the Context (while Renderphase, triggered from my own UIComponentRenderer). The Problem is, the FacesContext is a JSF2FacesContext Implementation and hide the delegate (FacesContextImpl). The Iterators oder getMessages() from JSF2FacesContext are all unmodifiable.

Could anyone get me a hint, how can i remove a Message from JSF2FacesContext (simular to the FacesContextImpl. getMessages().remove()).

Thanks
alex