I just picked up the DAM lightweight stock and there aren't any instructions on replacing it with the standard one. It doesn't have the mounting rail as it shows in all of the images, it's just the rear stock piece. I see two pins on the adjustment lever I could probably knock out to allow the internal rail to slide out. But, the spring used by the adjusting lever is under tension, and I don't see an easy way to get it back together after I take it apart. Any ideas on this?