drop mem down to 1400 or so, undervolt it. my 4gb rx580's get 39-40 at 1400mhz core, 1400mhz mem. undervolted to 1075 on core, 850 on mem. about 125-130 watts. My 570 will only run up to about 1300 mhz at +50% power. If you use overdriventool copy the fastest core state and voltage to everything but slot 1 and 2.
Did you go below 1075 on the RX570's with 1300 clock? I'm going to do some testing tonight to get this stable...
Yes, 1300 and 1075 worked for me, I had to undervolt the memory and drop the mem clock down to 1400 though. I get around 35-37 on my 570.