UPDATE...
the 43.7 was for Expanse
Just tried the same settings with ETH 38.5
You need blockchain drivers with HBCC enabled for 44+eth. But blockchain drivers are pain to downvolt. But it is possible!
@rednoW, would you mind explaining step by step how you are getting undervolt to work with the blockchain drivers? I've tried fiddling with command line switches and wattman settings and can't seem to get them to stick. I'm running 5x Vega 64 at the moment and getting 41.5Mh on the blockchain drivers but I'm running 960/1025/-10%/65C fan target so my power consumption is very high.