Prince's journey has been a long and trying one, both for him and for us.  We are making some progress with him though.  His main problems are that he stops with his feet all strung out, he lacks impulsion, and he doesn't know how to stop balanced.   He is just an immature colt, that grew physically faster than mentally. 

This pictures is an example of the unbalanced stop Prince makes.  See how far apart his feet are?  He can't engage his body from this position.  We are making progress with Prince.  He is doing a lot more balanced stops now. 
Lots of colts, that are big physically, have this sort of issue.  They just grow faster than their mind does.  Remember this when you want to buy a 4 year old and he is big.  A good place to go for information on this phenomenon is Dr. Deb Bennett's page on the Internet.