Okay perfect thank you. He has just started in to work i ggae him the spring n summer off. But i will most definitely be trying all of this:)
Agree with Brenna but also lost of transitions like wall-canter-walk and jumping will help.
You have to keep working him in both directions. Focus a lot on bending, and keeping his stride (especially on the left) open. Small circles, spiralling outward and back in will help, pushing him out. Also changing between a collected and extended step, so that he really has to work his bum muscles. Make sure you don't forget to work on the right muscle as well, even though it's the left that's underdeveloped