Clustering GoeRSS layer

I am using flexviewer 3.4 and try to use clustering for GeoRSS layer copying the code I previously have used successfully for feature layers, but it doesn't work for my GeoRSS layer:

<layer label="UN-ASIGN GeoRSS" type="georss" visible="true" url="http://asign.cern.ch/resources/georss/crowd_photo.xml">
<clustering mingraphiccount="1" sizeinpixels="80">
<clustersymbol type="flare"
alphas="0.2,0.7,1"
colors="0xFFFF00,0xFFA500,0xFF0000"
flaremaxcount = "10"
size="30"
sizes = "30,60,90"
textsize="14"
textcolor="0x000000"
bordercolor="0xb28f00"
weights="10,100,9999" />
</clustering>
</layer>

Additional, I would like to know if it is possible to change the GeoRSS symbol to have different color for various layers?

Thanks for any support to the issue.

Ivan Baehr,
UNOSAT