coccyx! My wife broke hers in the Army and it never healed right (she busted her *** for this country! hee hee) and actually has a VA disability for it. Lots of pain for her actually. For her the solution was not more padding under the coccyx or a different seat because the pressure will eventually build up. The answer was her riding posture. She had to train herself not to slouch too far back which caused her pelvis to roll back on the coccyx. She focuses on sitting more upright or even leaning a touch forward. No pressure, no problem.