More information on more efficient usage of PCC: http://forum.mikrotik.com/t/using-pcc-more-efficient/169215/4
Mind boggling, with three WAN and asymmetric distribution: http://forum.mikrotik.com/t/mikrotik-pcc-and-ecmp-load-balancing-script-generator-over-unequal-multi-wan-links/158034/4