It's not listed in http://chdk.wikia.com/wiki/CameraFeatures
, so you should try for yourself and add your results there.
Enable the override and take some test shoots with and without the override and compare histograms. If using mains powered lighting, use a slow shutter speed (like 1 second) or your results will be inconclusive. Try with minimum and maximum zoom settings.
Setting a too high value should not hurt your camera, it will probably just use the smallest hole it is able to.