Keep in mind that the block and tackle will shorten the amount of string pull, relative to the amount you pull on the rope.Easier to pull ,just have to pull it farther and compensate for how far the stationary pulley is from the bow.Don't forget to post video of you strining it. You could always give hime a small tree with nocks ,and a string ,and tell him when he braces that he's ready for a 200 lb.warbow.
Does he currently shoot traditional,and understand the concept, or is he just trying to prove a point. Set a new record ,maybe?