I have now run ~72 hours w/o any issues with 24 Vega64 GPUs(good and bad ones) mixed in 4 separate rigs ... CNR with core 1407Mhz /860-970mV , Mem 1080-1100Mhz/860-970mV.

I would say this is pretty stable setup. Pool side 24h avg hashrate fluctuates in the range 54,1-54,4 kH/s

--CL 19 --RAS 28 --RCDRD 12 --RCDWR 5 --RC 44 --RP 12 --RRDS 3 --RRDL 3 --REF 15600 --RFC 250

I am happy and have in my mind... "dont touch when things go smoothly".