Don't think its possible. Can you install DDWRT on it should it be supported by Tomato http://www.dd-wrt.com/wiki/index.php/Supported_Devices#Buffalo
yeah,looks like that Eko latest release DD-WRT builds work with Buffalo WHRG300N.Iam read about this in this thread. http://www.dd-wrt.com/phpBB2/viewtopic.php?t=46997 so perhaps Jon can add support for this router too