Join Date: Aug 2010
Location: Central Missouri
For lack of a better term, you've thrown her out of "balance". Some of these gaited horses are very sensitive to change.
It could the the weight or it could also be the hoof angle. You can compensate for weight a little by a longer rear toe, and a bit shorter front toe.
If she is tending toward a quicker release of the front foot(rack oriented) you might try a higher front foot angle, ie, slow the front foot lift down, and force the rear lift sooner(running walk oriented)