Not trying to argue but, you do realize the entire grill is countering the shelf dont you? plus much of the shelf is neutralized sitting over the axle,, or as you put it, fulcrum? adding 1/3 of the weight of the load on the shelf to counter the entire weights, hence, 8# is now 5.3#, with 2.7# added to the already weights of the grill itself, now increasing the counter weight (total weight of counterweight). Now if he hung it off the backside of the entire shelve, well without measurements that's a total guess.
Trust me, rigging and fabricating is more than looks like, but I will assure you 8# of chicken,,,, ON THE CENTER OF THAT SHELF, is not a problem, then add the insert weight and stainless frame to the kettle (your counterweight),,, well that's pretty much self explained.