I see it matching the Speaker volume (I rename hud.exe to ultraedit.exe for....reasons

)
Pic
OK, did a little more testing using and looking at the mixer.
With my game vols at:
Master = 100
Effects = 30
Ambient = 30
With Windows vol at 100%:
Hud.Sound.VolumeMultiplier = 1 //shows hud @ 30%
Hud.Sound.VolumeMultiplier = 2 //shows hud @ 60%
Hud.Sound.VolumeMultiplier = 3 //shows hud @ 90%
Hud.Sound.VolumeMultiplier = 4 (and up) //shows hud @ 100%
(With windows at my original 50%, those hud numbers are half - 15, 30, 45, 50)
So, again, if HUD can use D3 master as a baseline and allow us to just set our own multiplier OF that, I think we'd be good.
(I'm thinking of maybe a plugin that can toggle like 3 different levels of HUD volume so that you can adjust it without having to restart)