When I first started, I built a 42 inch barrel fullstock, .32 caliber 7/8. I only used three pins. The inletting was not the best, so it was bedded. One time I picked it up the from the bottom of the upper forstock, at a point that was in between two pins. It felt as if the stock had pulled away from the barrel. I repeated the action while watching. Sure enough, the stock was pulling away. I am sure it was due to the heavy barrel and a number of other "fit" problems but from that point on, I only used 4 for fullstocks 38 inches or longer.
Brian