You want a real play...here

[dddunn3d]

I'll set the stage: It's my first season umpiring(three years ago). I received a call the night before a 12u tournament asking to fill-in. As it turns out, I find myself on the bases in the championship game. I'm not bragging, etc. that's just the way it happened.

The sitch: R2/R3 one out, middle innings, defense ahead by a couple, infielders playing back.
B1 pops-up to a point about halfway between 2B and 3B right on the basepath. R2 starts running, gets a little past the point where the ball is coming down, realizes that there's a good chance he'll be doubled up, and retreats to 2B.
The SS sees the pop-up, but since he's deeper than normal he has to accelerate quickly to get to it. He takes about four or five full-speed steps, sees R2 crossing about six-eight feet in front of him, and stops completely. R2 doesn't stop after he reverses direction.

I ruled no interference. (I realize that for any of you to rule on this YHTBT.) In my judgement(key words to be sure) if the SS had continued to where the ball was coming down he would have had a play on the ball. R2 was clearing the area the SS needed in order to make the play. I think that the SS let himself get distracted by R2 crossing his field of vision.

Which leads to my question: What guidelines do any of you have when ruling on a play such as this? Is contact required in order to call interference? Or can the defense claim interference by distraction? Just how close do the players involved have to be to each other?