...
Read... So, it would seems to me that a 10~20% decrease in efficiency for large miners such as Cointerra and S2 is a known issue and unresolved .....

Not sure if I should stay in P2Pool with my Cointerra gears in this case .... sad

While the issue with the S2 has been well documented here, you are the first case of a problem with Cointerra gear I have seen.
Cointerra is specifically listed in the wiki as working well.
https://en.bitcoin.it/wiki/P2Pool#Interoperability_tableI would also like to hear from other Cointerra miners on p2pool.