:D:D:D
Hold still, and we will find out 
That would put you falling back first while trying to hold the Stinger vertically on your shoulder with the airflow catching in the tube - absolutely not stable enough, and you cannot fire the Stinger any other way.
Generally, without tracer and automatic fire (or a predictive gunsight) you are unlikely to hit anything while parachuting/falling/flying.
Unless you are Chuck Norris. Then the target moves to ensure that that bullet you fired hits it. 
Si
While Ranchoth is tumbling about trying to get into a stable position to fire, can I pull the ripcord, turn towards the target, shoot, mix a martini, light a cigar, throw the martini over my shoulder in favour of a good Scotch, ash the cigar, put on sunglasses, enjoy the site of my foe’s aircraft exploding into tiny bits, and land in the French countryside on a big bale of hay tended by a group of buxom maids, safely?
More likely, you will enjoy the sight of the Stinger engine lighting up, glory in the wonder as the flames race up the shroud lines, scream in pain as drops of burning nylon rain down upon you only to be replaced suddenly by the cool of accelerating air past your face, giving you a brief respite to think
Oh shit…before self-interring.
Si
Could I at least light the cigar on the flaming bits of nylon?
Actually, are you sure this would happen?
From the above descriptions, the boomy part gets shot out “for a few meters before the flight motor kicks in.” Since I’ll still be floating gently down—as opposed to the explody bit–won’t those few/fractional seconds put it slightly below me? Even if it’s still even with or slightly above me, how could it’s exhaust ignite the parachute but not the average soldier shooting it from the ground?
Basically, if someone could shoot from a standing position and singe neither brow nor mullet, why would the parachute ignite? In training, what do they tell to look out for in the immediate vicinity? Granted, they probably focus a lot on the many ways that you can put your eye out, but do you need to make sure there are no low-hanging branches overhead?
It’s so easy. Exit aircraft, open chute, aim, shoot, release now flaming parachute, open reserve chute, light cigar.
How high was I to start with again? I forgot.
I was actually wondering if this might be a valid way of doing this, rather than attempting launch during freefall itself. With an emphasis on not being basted in melting nylon.
They tell gunner to be sure of back blast area, no people, or things that go “boom” or “whoosh” like paint lockers on ships. Generally the gunners are in static positions, with primary and alternate firing spots and a known sector they are primarily responsible for. Obviously that sector should be devoid of low hanging branches and whatnot, and clear of things that make unexpected secondary explosions.
Providing mobile defense of a convoy makes that whole “clear field of fire” bit more challenging, but MANPAD (Man Portable Air Defense) Stinger teams are two dudes, one with the missile looking through the peep sights, and the other watching out for other things and helping the gunner gain sight of the primary target and talking on the radio.
This is going to be the best bachelor party ever.
I can’t wait for this Mythbusters episode.
that’s EXACTLY what I was thinking… how will Jamie and Adam do this???
…with chicks and guns and fire trucks and hookers and drugs and booze and stinger missiles!