Join Date: Sep 2011
Location: Germany- but not German =D
You need to keep the inside leg as a pulse to the horse, I would suggest slightly more weight in your outside leg (not so you're sitting to the outside, however) and think about taking your outside leg 'off' the horse, almost as though you are pulling him to the outside, using your outside hand to steady him so he doesn't drift, or fall to the inside.
Keep your inside leg long, and feel as though you are pushing him in to your outside hand, don't let your inside hand cross over his wither though, its a common thing to try and stear the horse to the outside with your reins.
Is he nice and supple in his back, and using his hind legs properly? See if he lunges alright on a circle, if so, then I would suggest its either rider error, or he's unsure of how to do it properly.
Hope this helps!