Blocking the plate

[Forest Ump]

I was working the dish tonight in a 15U Pony Game. OBR with a modified rule that no fielder can block a base without the ball.

R2, clean hit to right field. Play at the plate. Ball arrives as the catcher is going down to block the plate. Very fluid motion. The runner slides. The catcher has blocked the plate with the ball. He puts the tag on the sliding runner. No call yet. Ball falls out of catcher’s mitt. It rolls less than an arms length away. Catcher is still blocking the plate. Runner is trying to touch the plate. Catcher picks up ball and tags runner. I signal out. Coach comes unglued and wants an obstruction call. I ruled no obstruction on the first part because the ball arrived as the fielder blocked the plate. I ruled no obstruction on the second part because the ball was less than an arms length away.

I would like some opinions. Did I get it right? If not, please provide your reasoning.