The hook will “feel” fine for lighter weight that you can still hold with a double pronated grip, even if you are doing it incorrectly and not gripping it as tightly as you should. However, when the weight is greater than what your double pronated grip can hold, you have to grip that bar as if someone is trying to steal your paycheck in order for the hook to work properly. And with a tight—and I mean TIGHT—hook grip, you are smashing your own thumb to the deadlift bar. If you grab the bar with less than your tightest grip, the bar will smash your thumb as the bar is lifted, so now you have gravity, the barbell, and 700 pounds smashing your thumb. The tighter the grip of your hook, the less pain to your thumbs.