deleting text from collector-pane

Hi all
I have a collector-pane for logging, using (format collector-pane-stream ....) when writing to it. I would like to limit the size of the collector-pane buffer so that I don't run out of memory.
One way would be to use something like this when the buffer grows too big:
(setf (capi:editor-pane-text collector-pane) ...)
but is there a better way?
Thanks!
Sven