I'm sure others have experience with different saddles and their effect on
posting. My hit on it is from your body. I wonder if you are using your
extrinsic muscle to psot rather than the intrinsics. The extrinsic are very
lightly innervated, one motor nerve to many muscle fibers. Where as
intrinsics are more heaviliy innervated, one motor nerve to few muscle
fibers. What this means is that when an extrinisc muscle fires you get alot
of fibers working and very little control. We learn to move throught eh use
of the extrinsics, this is why babys are so jerky in their movement. (my
handwriting is still in the extrinsic muscles!).
I would suggest that you get a Fit Ball and try gentle posting on it. Just
roll forward and up. If you use the quadraceps to post you're using an
extrinsic if you can use the psoas you'll have more control. You might need
to get another person to coach you from the ground.
There are some simple exercises for developing the psoas.
jim pascucci
Certified Rolfer