As a hunter convert with the "duck butt" tendencies rather than slouchy tendencies, my hip flexors are the biggest enemy to the possibility of even sitting correctly. I suspect in the end my most effective position even after lots of yoga will include shorter stirrups and/or more of a chair seat than ideal to make up for tight hip flexors and to allow movement in the hip joints to follow my horse.
Do you have a chance to ride with a good biomechanics instructor or someone who really focuses on use of your body? I think everything I read above is correct, but part of your problem stems from not using your core correctly. The forward tip makes your seat restrict her, so bump bump won't even help as long as she can't go forward because your seat is stopping her from going forward.
My horse is a dressage diva so I don't have to be.
Originally Posted by katarine
If you have a fat gay horse that likes Parelli, you're really screwed
For what it's worth, your shrimpifying can't be all that terrible. I knew this poor lady who was so terrified of her (bombproof) horse that she would -literally- curl up into the fetal position at the slightest imaginary problem. And therefore fall off. At a plodding walk.
I think the bat or crop idea is a good one. If you're having position issues, a long whip can get in the way, accidentally smack the wall of the arena or another horse... with a crop you don't have to switch hands every time you change direction if you don't want to.