Isn't the ball terribly unbalanced? Trackball users often "throw" the cursor, where the ball rotates freely at speed, and it would induce an awkward wobble with an unbalanced ball.
I'm an avid trackball user, and this is one of the key attractions. I can flick the cursor from one side of my dual 1440p monitor set to the other, very quickly. It also works quite well with triple monitor setups.
