I've noticed in reaper, if you tell it to run 5 threads it says it starting 10! Don't know if that has anything to do with it??
There's definitely not enough resources at 10240 gap 2 to run 5 actual threads on a 7970, and since the values don't line up with raper, who knows what it's doing, so long as we get good performance... I've lost interest at looking at the raper code itself since I got the kernel working well.