Yes! I have been toying with Wattman and doing just this. So far I am at:
GPU P6 1537 MHz @ 1050 mV
GPU P7 1612 MHz @ 1100 mV
HBM 900 MHz @ 950 mV
Power Limit -50%
Default Fan Curve (85 Max, 74 Target, Fan Auto)
I remember that R9 thread too and tried one which yielded similar results in my...