Well, he is wiping over and around the ball quite a bit so where his stroke ends in my opinion isn't really the issue. I just think his shot could have more bite or at least play the variety by hitting through the ball a little more rather than around it.
That's basically the effect I was envisioning with my advise.
By the way, do you have video material of yourself playing? Your backhand motion looks really unorthodox in your signature, I'm wondering how it looks in action