Everyone is completely different as you would imagine. Personally the only pain i have is the skin stretching near the left pinsite by my knee but the soft tissues seem to be taking it well. I am at 6CM. Depends on your pain tolerance and even things such as distraction rate. Once you reach about 5cm or so you will more or less be able to feel what it's like to do more. In short it is not easy but everyone is individual so only you can tell once you do it.