The only time I needed that much bipod was trying for the mile gong, but it was at a significantly elevated position relative to the firing position. My .243 was too high for my rear bag with the 9-13" bipod for most of the roughly flat shooting throughout the course. The sandbag you see under my rifle in the first photo of my write-up is to help me load it, not to increase the height. My subsequent experiences have led me to find a 6-9" works the best for me out to 1000 yards with the legs extended one notch. It's probably a matter of individual ergonomics and ballistics.

As Charlie says notches and a swivel are must-haves for sure.