EDIT: Let me clarify, because I realized it's possible to misinterpret what I said there. I'm not suggesting that the move in pyong ahn sam dan is an elbow strike, but rather that a similar principle is involved.
To break down what happens in that part of pyong ahn sam dan:
(1) Your opponent punches; you block the punch with your kick
(2) Your opponent punches again; you deflect again, this time using your elbow, turning with your waist for power, then smack him one on the forehead.
There are other interpretations, I'm sure. I'd like to think that, if your opponent doesn't go for a second punch (or even if he does), that elbow could be turning into a pal koop kong kyuk to the temple. It'd require a deviance from the actual motion of the form, but a lot of these things are hidden like that anyway.
Anyway...to clarify what I mean about having a narrow angle to your elbow, not only does it give you a couple inches more reach, but it makes it more sturdy. Try hitting into something with a loose elbow like that. Try tensing your muscles as tight as you can, while still keeping your fist planted on your hip. Then bring your fist up to your ribs, crank back your waist, and let fly. This isn't a square dance here; it might be slightly more comfortable to have your hands on your hips, but it's going to hurt you, no matter how tense you think you are, because the hips only provide power. You have to have something that's going to stand up to whatever it has to hit, whether it be a fist coming at you or your opponent's side, or whatever.
Those who know it, think of jinte (jindo/chinte/whatever), after the second time you drop into horse stance. You don't think you're just blocking something with those twists, do you? You're breaking out of a grab, so you're dropping into horse stance to loosen yourself and then slamming your elbows into your opponent's sides so he lets go and backs away (unless he wants more pain). You don't want your elbows that wide apart for something like that. You want them in close to deliver swift, fast strikes.
In regard to the "collapsing" of my shoulder, I'm not throwing with my shoulder, so I see no reason for it to collapse. Elbow techniques are one of those areas to which I give special attention when I'm practicing before class. If you're throwing it with your shoulder, you're doing it incorrectly anyway.
Again, all respect to my seniors.
Tang Soo! (again)