Setting up the right leg length is important. For the Epic surf ski range the hump design in the cockpit is shaped so as you pull from the hip and rotate your torso the back of your knee will just touch the hump at the end of the stroke.
If the back of your knee touches the hump too early it means your foot plate is too far away from you. If the back of your knee doesn't touch the hump at all, your leg length is too close to you.