>horse. It didn't fit me very well because the stirrups are hung far
>forward and the twist is wide. That meant I was always loosing my
>stirrup because I couldn't get them back far enough and my left leg
I had the same problem on one of my instructor's new horses.
There was no way I could sit properly until we discovered that
it wasn't me doing something wrong--it was the saddle fit! A
lift-back pad made a big difference because all her other english
saddles were being used that day.
It may have been that your fit wasn't balanced, ie, the deepest part
of the seat was too far back because of the horse being a little
uphill (or wide/muscular withers) more than what it was made for.
The horizontal distance between the deepest part of the seat and the
point where the stirrups hang is important for a secure and correct
position as well as riding style/activity.