Lead shot VR4jr's

I finally bought some lead shot, 2 bags at 25 lbs(which seems like a small bag for such a big cabinet). I am going to attempt loading the speakers this week-end. Those of you that have already done this, is it a compartment that holds the shot, or does it fall to the top when you load it and then bounce around and hit everything when you flip them over? I'm sorry if this is a stupid question, but I would appreciate it if you would share your experiences and what you would do differently, given the chance. Did you push a plastic bag inside to be a liner? Did you notice an immediate improvement? Was it worth the effort?
Thanks
jeff