Rules of Forward Lean Club:
1. You never set the cuff's forward lean greater than what your ankle (dorsiflexion) allows. If you do this, it will strain your Achilles, cause your heel to lift, cause your foot to slide laterally inside the boot, and you will hate life. If your ankle tops out at 15°, do not set your boot to 17°. Don't know what you need? See your local boot-fitter for a range of motion assessment.
2. More forward lean creates a more aggressive athletic stance. This is good for skiing faster, skiing steeper terrain but it can be hard on your quads.
3. Less forward lean creates a more upright stance. This can be more relaxing, but a greater tendency for your weight get more rearward. If someone has a limited range of motion, you most often want to position the cuff more upright to avoid rule #1. Also, a cuff should be positioned more upright when a skier has a big calf muscle. A big calf essentially pushes you forward, increasing your effective forward lean.