I tried a lot of options, but I cant achieve more than 860h, maybe it's because of memory hynix (with samsung memory peoples report 1000h+), I'll have to go back to SG miner. RX 580 8gb with Hynix have 970h. 
The same situation, but i cant even reach 860 h/s. Recently i bought 5 Asus Dual OC RX 580 8gb with hynix memory. I flashed it with uber mix straps, in stock it showed 570 h/s, after flashing - 772 h/s. Changing cclock and mclock hash only a slight effect. With cclock 1100 it shows 760 h/s and with 1360 - 772 h/s. Exactly the same situation with mclock. MSI Afterburner and wattman show that clocks change correctly. I also tried to change -dmem and -h, -dmem 0 decreases hashrate to 550 h/s, changing -h has no effect. MB - BIOSTAR TB250-BTC.
I also have another 1 rig that runs 3 Asus Dual OC rx 580 8gb with samsung memory and 2 asus dual oc rx 580 4gb with elpida memory.
I was able to get stable 1020 hashes with 8gb version (cclock 1330, mclock 2000) with samsung memory and 925 hashes with 4gb version with elpida memory. MB - AsRock Z170 Extreme 3.
I tried differrent miners with different settings - no effect, the hashrate even lower.
Mb smb can help me with an advice?