I wrestled with whether to go for the locking or not locking version, but also the height. In the end, I decided to go with the 9 to 13, rather than the 6 to 9 version because of my hunting conditions. I also went for the 'S' version and bought a pod-lock from E. Arthur Brown. Because I could adjust the cant with the 'S' version, I went for the notched legs.
Who would have guessed there were so many options for a simple device?
The only thing I am presently concerned about is whether I should have gone for the shorter bipod. If it turns out I need a shorter one, I'll just have to buy another and then have two!
Thanks for advice.