Can SizeI use 40 oz bean(like a red kidney bean,etc) for 14 lb turkeys and for 21 pounders, I use the 46 ounce V8 juice cans. If you want to be safe, have both cans handy so that you can make it work for the 19 pounder. Its the diameter and the size of the turkey opening that can vary.
I always pull the skin over the neck area and put a skewer through it to keep the moisture in. Also, you may need to put a skewer between the legs and tie to keep it stable. I keep it right in my broiler pans while I smoke so that I can siphon the drippings and baste it occasionally. I add some butter, beer, or whatever to the pan to give it a head start on accumulating liquid/flavor:-)