Hey, try using -g 2 and optimized from the start again.  I couldn't get above 600 until I moved to g 2.  when I did that though I had to start at the beginning and optimize the settings. 

Here is my conf settings:
"api-allow" : "W:127.0.0.1",
"api-listen" : true,
"scrypt" : true,
"auto-fan" : true,
"gpu-engine" : "0-1006",
"gpu-fan" : "0-85",
"gpu-memclock" : "1700",
"gpu-memdiff" : "0",
"gpu-threads" : "2",
"gpu-powertune" : "0",
"gpu-vddc" : "0.000",
"intensity" : "13",
"temp-overheat" : "85",
"temp-cutoff" : "95",
"temp-target" : "75",
"vectors" : "1",
"worksize" : "256",
"lookup-gap" : "0",
"shaders" : "0",
"thread-concurrency" : "22148"