in my tests, 0780 & 4f81 yielded the same result - so I think they are both very close, if not 400mhz

I can confirm that my overnight test seems to be a success... averaging 197GH @ .59% HW ... which is higher than the 375mhz setting, but lower than 400mhz
I dont know what the exact equation is for figuring out hashrate based on clock but the numbers match up with 512*mhz = mh/s
Based on that equation, 5e82 seems to clock in right around 384mhz

Also, if someone wants to experiment w/ the xx83 ranges ... I imagine the values will start in the 6x83...