This morning I noticed there was a new SimpleMining OS image available to download. The file name is SimpleMiningOS-NV-RX-v1182-4.17.14-amd18.20-nv396.51.img and it includes Nvidia driver 396.51. I've been waiting on this update in order to try out ethminer 0.15.0 that was added to SMOS last month. That version of ethminer doesn't work with the previous image that includes Nvidia driver 390.67.
Right now I'm running one rig with the new image and mining ETH with ethminer 0.15.0. The only difference I've noticed so far is that the total hashrate fluctuation has narrowed to less than 1 Mh/s. The total hashrate on the same rig running the previous image and mining with ethminer 0.14.0 would fluctuate by 1-3 Mh/s.
I haven't adjusted any of the overclock settings on the rig running the new image and mining ethminer 0.15.0. If it runs for a week without a restart or any other problems on the same settings as when it was running the previous image mining with ethminer 0.14.0, then I'll start playing around with the overclocks.