Getting about the same (27.3-27.4) on Win7 with 16.9.2 drivers.  Running 1100/1950, using the 1500Mhz strap.  Also had to boost the power limit to stop it from throttling.  Can manage a 50mV undervolt (GPU-Z shows 1.1V VDDC), but 75mV isn't stable.  Gonna do a bit more experimenting before trying it on my Ubuntu 14.04.4 rig.