Stratum and Hashrate question.

So I recently switched over to mining Ether. I downloaded the openCL ethminer and the ethproxy from Dwarfpool. I have have a couple questions that I'm hoping someone can help me with.

• My rig is 4x R9 270x cards. I'm getting about 56-58MH/s. Is this average, if not what are the common flags to tweak performance?

• Right now I have stratum running with the host 0.0.0.0 and port 8080. On the miner batch file i'm running -F http://127.0.0.1:8080/. Is that the correct config? I seem to be getting accepted blocks. Do I run the stratum on all the rigs on just the main one and then tell the rest of the rigs to use -F http://<main rig static ip>:8080/ ?

Hope this all makes sense. Thanks in advance.