I'm looking over the different models, and I've noticed some have the K-tab placed on a higher axis than the P-tab, some are even, and some have a higher P-tab. What's the advantage of this? I imagine having the K-tab higher up makes it more responsive when you're on your side and curled up, and a higher P-tab is better for laying on your back and moving your hips up in a thrusting motion. Maybe also for taking a walk with.