what about your settings with 270 please?
"intensity" : "3,3,3",
"vectors" : "1,1,1",
"worksize" : "256,256,256",
"kernel" : "heavy,heavy,heavy",
"gpu-engine" : "1200-1200,1200-1200,1200-1200",
"gpu-fan" : "0-85,0-85,0-85",
"gpu-memclock" : "1100,1100,1100",
"gpu-memdiff" : "0,0,0",
"gpu-powertune" : "0,0,0",
"gpu-vddc" : "0.000,0.000,0.000",
"temp-cutoff" : "95,95,95",
"temp-overheat" : "85,85,85",
"temp-target" : "75,75,75",
"api-mcast-port" : "4028",
"api-port" : "4028",
"expiry" : "120",
"failover-switch-delay" : "60",
"gpu-dyninterval" : "7",
"gpu-platform" : "0",
"gpu-threads" : "1",
"log" : "5",
"log-dateformat" : "0",
"no-pool-disable" : true,
"queue" : "1",
"scan-time" : "60",
"heavy" : true,
"temp-hysteresis" : "3",
"shares" : "0",
"kernel-path" : "/usr/local/bin"