You can re-position one of the weights on the shaker to make the two weights less out-of-balance. They are both oriented the same by default. If you rotated one 180 degrees, they are fairly balanced and the shaker doesn't do much, but rotating one about 90 degrees is a nice middle ground. I did that on my Metallica, as that shaker was much more violent than those in my other machines. There is a dimple on the motor shaft where the allen head set screw rests, but I haven't had issues since rotating mine off of this dimple. Just make sure the set screw is tight.

Also, I just fixed a rattle issue on my Iron Man shaker that was not caused by the orientation of the weights. Rather, the motor itself had come loose from the mounting bracket. I used some metal strapping to hold the motor down tight to the bracket and that solved the problem. Let me know if you would like some photos of this. Good luck!

Here's a pic. I moved one of the weights 90 degrees for illustrative purposes. On this particular shaker I actually have them set in the default position. You can see the metal strap that I used to hold the motor to the bracket.

Shaker.JPG