How long should I marinate Chicken?
Marination is generally a surface treatment, so the thickness of your chicken is  irrelevant.  Really, the only thing that can penetrate is salt, primarily because of molecule size.  You can read a good explanation here.  I would say you're good with the 2 hours, but as you will see when you read the article, you might not even need that long...or you might want to rethink the marinade altogether.