At this moment it is impossible to use the full txpower of the WN570HA1 on both bands (2,4Ghz and 5Ghz).
Possible txpower at the moment:
2,4 Ghz --->24dbm (should have at least 27dbm)
5 Ghz ---> 11 dbm or 13 dbm (can`t remember right now)
Is it possible, that the device uses an external amplifier which has to be activated via gpio settings?