The size of the hook doesn't much matter. You're simply using an object to administer a tactile cue to let the snake know that a handling session is about to begin. What does matter is that you cue him the same way each time so as not to confuse the poor fellow.
Another idea is maybe to just let him bite you a few times next hissy fit he throws. There are snakes that will always seem to want to draw blood and there are those that are just nervous animals testing the boundaries of a new relationship. Some will calm down faster when they realize the bite is ineffective. I reckon better to find out which category your boy falls into now rather than after a couple more years of growth.