Clean changes and Piaffe

Woo Hooo!!! A friend recommended a book "Twisted Truths of Modern Dressage" by Phillippe Karl. In reading this very well presented and informative book I noticed he was describing my horse. Kalae is hollow to the right. Her right hind escapes to the inside when cantering right. She is stiffer to the left. I struggle to counter canter and now she changes late behind. I have been stuck for 2-3 years without advancing beyond 3rd level. I applied Phillippe Karl's recommendations and immediately I could counter canter on a 10 meter circle. My horse was no longer changing on her own but waiting for me. I have been working on his exercise for changes and have gotten clean changes which are jumping from behind. I have also been working on his exercise for Piaffe. A few days ago while on the trail she got very excited when the dogs started bounding out of the reservoir and running toward us. Perfect. I put my legs back and we had a Piaffe. I patted her and tried again. I got 10 Piaffe's on request. Yesterday when the neighbors dog scared her we got it again. She has gotten the concept down. Coupled with a good canter pirouette I can now imagine perhaps actually wearing my shadbelly coat soon. I down loaded the FEI 2009 Prix Saint George test from www.fei.org and have been memorizing it. :)