How to aim stinger on expert mode?

[Bulldog72]

Topic says it all - if playing on lower difficulty setting I get this nice green rectangle around some intended target, wait a few seconds for the beeping and locked sounds and press fire.
But how does this work on expert mode?
I do hear the sounds but I have no clue on which of multiple possible targets the stinger actually locks on... how does an "expert" do it?

[Beagle]

Topic says it all - if playing on lower difficulty setting I get this nice green rectangle around some intended target, wait a few seconds for the beeping and locked sounds and press fire.
But how does this work on expert mode?
I do hear the sounds but I have no clue on which of multiple possible targets the stinger actually locks on... how does an "expert" do it?

By aiming exactly at the target...not at another. And when were already on topic...best results in ArmA come from head on shots at low range. (500m) Perpendicular shots simply miss most of the time.

[Muerte LOL]

Quick shot works well for me. Get the target in site when close, right click, fire and do so quickly. Seems if I wait I miss more often. I'm not sure if it takes time for the target (chopper etc) to detect the lock or if it's instantaneous but no hesitation gives me best results.

[Lonestar]

Just use the sounds and be quick.