Here is my settings for my 290's cards:

"api-allow" : "W:127.0.0.1",
"api-listen" : true,
"api-mcast-port" : "4028",
"api-port" : "4028",
"expiry" : "120",
"failover-only" : true,
"kernel-path" : "/usr/local/bin",
"log" : "5",
"queue" : "1",
"scan-time" : "1",
"auto-fan" : true,
"auto-gpu" : true,
"temp-target" : "75",
"temp-overheat" : "85",
"temp-cutoff" : "95",
"temp-hysteresis" : "3",
"lookup-gap" : "2",
"gpu-threads" : "1",
"gpu-engine" : "1100",
"gpu-fan" : "0-85",
"gpu-memclock" : "1500",
"gpu-powertune" : "20",
"gpu-vddc" : "0.000",
"intensity" : "20",
"shaders" : "2048",
"thread-concurrency" : "24550",
"xintensity" : "0",
"rawintensity" : "0",
"failover-switch-delay" : "60",
"no-pool-disable" : true

Gets me around 3.2-3.3 Mh/s per card.