It is hard sometimes with stallions that have been gelded late due to the fact of habit not as much a dominant factor but habit.

Stand firm and carry a big stick. Oh and wear sunglasses so he can't see your eyes get really big! Just kidding but I truly feel they can tell when they have the upper hand.

P8nt is right on track. Find the source and I am sure you will.

Let us know what the answer turns out to be.