Give something like this a try.

"intensity" : "19",
"vectors" : "1",
"thread-concurrency" : "38912",
"gpu-engine" : "1050",
"gpu-memclock" : "1500",
"gpu-powertune" : "20",
"gpu-threads" : "1",
"worksize" : "256",
"scrypt" : true,
"kernel" : "scrypt",
"kernel-path" : "/usr/local/bin",
"lookup-gap" : "2"

7950's appear to really like a high TC.