I am short.. and my toilet is a regular size. So, from what you and the others are saying, it sounds like the nine inch one is best. I am also very active and flexible. Bubba.. where to you live? Want to sell yours? Although I suppose shipping could be expensive and a hassle.
I am wondering if Bed Bath and Beyond sell it since they return everything if you are unsatisfied. I will call them later today. It does sound like it's worth trying out to avoid all the straining I do.