Amumu Stuns

I main amumu support and it works fairly well. the CC factor is really important to the play style. but i have a big problem, my stuns dont work the way the should. Lets say im against a tristana and i Q her while she is mid flight. I will be pulled to where she was when my Q contacted her where as she will still go to her target location before being stopped. this makes my CC potentially nonexistent. the same goes for my ult. And this behavior isnt even consistent with other champions, for instance, if Nami were to land her Q on tristana mid flight, then tristana would be caught in the bubble then and there. I would really apreciate it if you guys over at Riot could look into this because it often can mean the difference between a successful engage or wasted spells, and consequently, it can also mean the difference between victory and defeat