@sunvalleylaw interesting idea of working on the end of the turn. I have tried this and I'm not sure that it is actually possible as you would like it to be - too much needs to happen before you get there.
If you really want to work on the finish of the turn you need to decide what that should look like for you and then remove as many variables as possible, For me the end of the turn is about 4-6ft before the white water - at this point I want to be balanced in the middle of the ski, as tall as possible with my upper body as high up off the water as possible. I will have already collected the handle and the line will be tight , power triangle engaged, ready to accelerate. - please be assured that this very rarely happens but it is what I am aiming for.
To know when you have got it right you need to be able to "feel" what it's like to get right - at least once :)
I would recommend that you get away from the course and free ski - look at seths "whips" the point at which he accelerates is the end of the turn.
CP s video is great and I had the pleasure of skiing with him and "Arnold" last month. It was windy so i took a free-ski set, with CP coaching, working on just this. Really "feeling" the balance into and through the turn.
If you find free skiing challenging then all the more reason, probably means you are skiing point to point rather than "feeling" the rhythm with the boat and your position on the ski. There is absolutely no reason to take "hits" freeskiing.
Hope it works for you :)