The shim actually works behind the front snap ring to pull the shaft forward to take up the play. I only had a 40 mm id shim that would not go over the splines. I had to get a 50mm id shim. And yes, it is better just in front of the dog ring which I can now do. I was concerned about expansion from heat and putting too much stress on the snap ring behind the dog ring. I know there is still a slight amount of play but it's smaller than I can measure in situ. I don't want to pull this thing completely apart for a 3rd time in 3 weeks
And thank you!