I got very stable hashrate on the rig with 6 cards with v0.5.6! Thank you! Previous versions were a lot unstable.

330-335 Sol/s GTX 1060 6GB (+180/+550/88%)
480-505 Sol/s GTX 1070  (+180/+550/88%)
620-630 Sol/s GTX 1080ti (+167/+500/92%)