If we now go back to the mechanics of the hair rig: The fish sucks in the bait, and attempts to spit it. The bare hook pricks its lip and it “bolts” off. Now with a heavy fixed lead in place, as the fish bolts the weight of the lead pulls the hook more firmly into its mouth and the fish is on before you have even seen the bite. To achieve this you need at least 2 ½ ounces of lead and I prefer 3 oz or more.
https://www.ontariocarpfishing.com/carp-fishing-made-easy.html
(I don't know how to choose, I listened to this person.)