Well today I opened the big arena doors and that seemed to put the wind up his butt slightly so he was more forward than normal. He was trotting round, his pace was pretty steady, not really rushing but also not the pokey fool he usually is and all of a sudden he got really light and springy and he just felt great. I've been trying for a while to get him more forward so he can use his back end better and get under himself more, and I guess I had just the right amount of pressure on the reins and he had just the right amount of impulsion and it all came together.
The great thing is not only did it come together but it stayed together, he felt more balanced at the walk and when I asked for a trot transition he didn't fling his head up and rush into it, he sprang into it like a graceful gazelle!
This great leap in his work today did unfortunately make his other flaws stand out more. For instance when he's tracking clockwise around the arena he can stay pretty well balanced through the corner and through 20m circles but when we change the rein he flexes his neck to the outside and cuts the corners and does egg shapes instead of circles. Albeit today he was springy and forward while doing those egg shapes.
So what can I do better in my riding (i know i'm probably causing this shoulder dropping and outside flexion) to help him flex better and not drop his shoulder? Can anyone recommend exercises we could do to supple him up more on both sides equally? He's been feeling a little stiff on his left side, I do carrot stretches with him.