I have a 18.9 full packer which will probably be 16 after trimming. I am planning 270 on my WSM no water in the pan. So I am struggling about what time to start it today. Originally I was planning for a 20 hour cook so I figured I start at 6 pm this way it will be done at about 12noon Two hour rest ready by 2 for lunch on Sunday.or should I start later?