Ethernet OAM BCPs Please are there any yet???

Hi Are there any best common practices for the CFM levels use Since my pure Ethernet aggregation layers are small I believe I only need two CFM levels I plan on using Level 5 between CPEs managed by us and Level 4 between Aggregation devices -that's where MPLS PWs kicks in So leaving Level 7 and Level 6 for customers and carrier-customers respectfully -would this be enough please? I'm also interested on what's the rule of thumb for CCMs Frequency, Number of Packets, Interpacket Interval, Packet Size and Lifetime for the particular operation Thanks a lot for any inputs adam