I very rarely weigh mine generally because if you've made the wrong choice of shot then your gonna miss!!!
I've not weighed any this year for any comp however i weighed a tin the other day for Bisley on Sunday as you can't win any shots back due to little wind etc, and they ranged from 8.14 to 8.76.
Not weighing them doesn't do any harm i just think you are mentally in a better place for the competition
FT WORLD CHAMPION 2016!!!