I have yet to try with cantering, due to I throw him off balance while cantering, and he trips (because of me...not a soundness issue). I will be trying maybe tomorrow with cantering while collected.
He's a stubborn boy, took alot of muscles and persistance to keep him collected, but finally he gave up trying to fight haha. By the end of the workout he had a nice sweat, and he seemed actually less tired than he used to be. So his endurance is building up also.
Tomorrow I'll try getting him collected the whole time