Spotting the ball, close to line-to-gain

[jTheUmp]

(Assuming 4+ man mechanics)

What mechanics should be used when the ball is spotted close to the line to gain; ie, when you think there will probably be a measurement needed?

Usually, I've seen the wing official mark the spot with his foot as normal, and have the U (or whoever) hand the ball to the wing to set down where he thinks it should go. However, I've had a couple of people tell me that the Umpire should set the ball down where he thinks the ball should be based on the wing's mark. As an Umpire, I'm a bit leery of doing so because any place I set the ball could be a couple of inches off from where the wing thinks it really should be spotted.

What say you?