you can pass all Properties to configure the JChannel via TreeCache.setClusterProperties(String). This is exactly the String that is passed to the Constructor of JChannel and allows to set whatever attributes you like for any protocoll on the JGroups stack you define.
See JGroups-documentation for details.
But this property is for the JChannel and has to be set using the setOpt() method of JChannel.
I don't see any configuration to set a property of JChannel directly.
done (in the CVS)