Hi Jimbo!
I have a PBV5 COMP. Many times I just let the water pan catch it all. But, mybwife makes a really good BBQ sauce and she uses pan drippings so I save her some. Her sauce is fabulous ( it doesn't have a shelf life like Cackalacky vinegar sauce.
If you use a catch pan it is advised to keep the distance 4" or greater below the meat you are cooking (top edge of pan to bottom of roast. Any closer and steam will be cooking the roast instead of the smoke.
I know some guys that place the pork butt in a 4" hotel pan start to finish, but I never do it that way. That method is to much like a counter top slow cooker.
Alton Brown has a scientific video about the effects of a pan under a roast.