[2312222]

From FactionUnit.ini -> AmericaParachute:

  Behavior = ParachuteContain ModuleTag_05
    PitchRateMax = 60           ; deg/sec
    RollRateMax = 60            ; deg/sec
    LowAltitudeDamping  = 0.2   ; how much to damp swaying when we get "close" to the ground
    ParachuteOpenDist   = 25.0  ; how far we have to fall 'till we open our 'chute
    AllowInsideKindOf   = INFANTRY PARACHUTABLE
    ParachuteOpenSound  = ParachuteOpen
  End

Look at "ParachuteOpenDist = 25.0". Change it to a higher value, that should give you a nice H.A.L.O. paradrop.