Has anyone damaged the box with the hammer trick?

It works!    Just get that puller as tight as you can, without breaking the puller, and use a small sledge (3lbs or so, The bigger the better and not a weeny ballpeen) and hit the large surface of the arm towards the front of the truck. It should just pop right off. I've had plenty of stuck arms in the past and this works everytime. You may have to repeat the process more than once until it's off. Good luck.