Thanks everyone. I will practice my posting again tomorrow. I worked so hard to sit the trot in my Western saddle I am just as confused at why my rearend isn't glued down there.
My instructor was pleased with my legs and arms until I started getting tired. She mentioned she could tell my balance started to faulter after we had been working at it.
I am holding the "up" beat too long... the saddle is smacking me in the rear and then I down into the saddle for the second smack.
I'm watching youtube videos of people posting to see the count better.