Helical gets the arrow spinning so it stabilizes better in flight. Makes BH tuning alot easier. FOC- Front of center. Having slightly more weight toward the front of the arrow is desiredfor accuracy. Most hunters strive for between 10%-15% for optimal flight. Basically the front of your arrow should be heavier by a certain percentage than the back half of the shaft. You will see some guys going as high as 25%, although that is not necessary. Hope this helped.

Shane