Just my personal experience but I can open mine fine with the thumb studs. Sure, it has a heavy detent because it's supposed to rocket out with the flipper. However, you can get it to fly out extremely fast with the thumb studs as well. That detent is great. You just need to know the direction you need to push on the studs exactly and it helps to have a thick callus built up on your thumb from opening tons of knives with hard detent and closing tons of frame locks and liner locks. I can easily get my 560 to slingshot out with the thumb studs. If the detent is really too, too hard, you can always take the lock bard stabilizer off and bend the lock bar over a little bit at a time so it doesn't push so hard on the blade, lowering the effect of the detent. However, there's got to be enough "spring" in the lock bar so that it goes over enough to fully lock into the blade tang. There should be plenty of room to set your desired pressure before you have bent it too far, though.