"helo high" is not 50,000 feet, it is a bit higher than helo low. Think 500 feet or so, maybe 1K feet. Helo low is the sort of altitude we were inserted by Pumas on Salisbury Plain, as we went round below the hills you could swear you saw the rotors decapitating rabbits on the slopes
!
Easily reached by ATGM - and if ATGM are plinking you it is because you are hovering up there giving the OPFOR a nice target. Once you get up to speed (2-5 hexes travelled) then you are travelling too fast for ATGM engagement or being bisected by tank gun APDS etc.
Cheers
Andy