I've had mine for a few weeks now, and I found myself controlling the ball with the middle of my fingers where the second joint is. It's solid enough that I can control it, and I can scroll the wheel without moving my fingers. Occasionally, I'll roll the ball where my finger between the first knuckle and second knuckle sit and control it there. Ultimately, I'm moving my hand around a lot more, which makes my hand feel pretty comfortable actually.
I still prefer the Slimblade when it comes to scrolling though. I'm not quite as constricted to how my hand rests on the ball to scroll, so I can control the ball and scroll more freely, opposed to my CST, where, if I wanted to scroll, I have to make sure my fingers are completely extended