While testing between a SXT AC SA and SXT AC indoor I see plain 802.11ac is working more reliable and faster than nv2.
Just do UDP tests between this two units. With 20 MHz both protocols are stable but plain .ac is 20MBit faster. With 40MHz channels nv2 spikes up and down while plain .ac gives reliable 250-280MBit/s one way.
Seems nv2 needs some tuning for .ac.