Well, GMMAT, since you don't know anything about field archery, there's no basis for you to understand what I'm trying to say.
Some background on the game... You shoot 4 arrows at each of 28 paper targets on butts set along a trail, marked distances from 20 feet to 80 yards, and everything in between. Even yardages, odd yardages, and depending on the course, uphill, downhill or even sidehill. Most of your shots will be between 20 and 60 yards, so you've got the 5 pins you're allowed in bowhunter freestyle class set at even 10 yard increments from 20 to 60.
If you've never been shown how to do it, you wouldn't be able to imagine double stacking your pins in order to hit an 80 yard target. It's an adventure trying to hit a target when your 60 yard pin is actually aiming at an imaginary point in a clear blue sky. Or, if you're lucky, you've managed to locate a leaf on a tall tree behind the target to aim at. All the while trying to allow for that @#$! ever present 25 mph crosswind....
And sometimes it works out that you come on that 80 yarder for the last target, after you've already shot 108 arrows for the day - not counting warmup and sight checks on the practice range - and you've still got these last 4 arrows to shoot to finish the round.
Guys who only shoot 30 arrows in a day's time at 40 yards max for 3D simply can't fathom it. You ain't never done any serious pin stacking until you've done a round of field archery....
You know, I've got the greatest respect for Len and the other fine archers who've responded. But I still can't see how centering a round pin guard would help one whit with putting the arrow where I want it. Maybe as an interim form check? I can visualize that, but not the final aiming. The pin is the aiming reference, not the guard. And I still say once you focus on that pin your eye is going to naturally center it up in your peep whether you will or nill.
That said, I've been feeling the need for some variety in my shooting lately and I've been playing with my sights for a few weeks. Now I've a notion to take off my multi-pin sight (rectangular pin guard

) and put on my single pin slider. Might even go so far as try and locate a good sight bar and scope fairly cheap and maybe even a V-bar stabilizer rig. Haven't shot THAT way in a heckuva long time.
Edit:
Len, you're right. Hunting is 98% of the archery market these days. That's unfortunate. These youngsters are missing out on so much by not shooting tournaments. But I do not accept that tournament shooting is all that different from hunting. The goal in both is to put that arrow exactly where you want it. The only reason most of us ever shot tournaments was to help us be better shots in the woods. And it works.
I've also seen a lot of these youngsters struggling with trying to do things the proper and updated way. When I've shown them some of my old-fashioned techniques they immediately got it and the frustration was over with. As has been most forcibly shoved at ME through this thread, I'll give it right back.
One size does NOT fit all.
I have no desire to confuse anyone, but rather want to let them know that there really are different ways to do things and it's okay to experiment. And just because it's old fashioned does not mean it's not worth trying.