Milter-greylist

All,
 	We use milter-greylist 4.4.3. We plan to upgrade later this 
summer. I want to evaluate a few DNSRBLs that are cached locally. I am 
interested in understanding which lists have more bang for their buck. It 
would be benneficial to write a meta DNSRBL rule that was positive if it 
was on both lists and then if not to continue list evaluation. Has anyone 
ever done anything like this?


Thanks,
Jonathan