I did hack it and I thought it was pretty straightforward. Been working for me great for a little over a year now. I actually found someone else who hacked the Crystal Trackball, and they helped me out. They even sent me some pics showing how he mounted the trackball. Actually, the hack I did involved just using the PCB of the trackball. I needed to get a Happ mounting plate and Happ 2-1/4" Top Bracket and a 2-1/4" trackball ball. I do not think replacing the trackball ball was required, but I was told getting a 2-1/4" from Happ really fits nicely....and it does. The only real thing you have to do is get yourself a square piece of wood and drill holes in the spots you need to and then mount the PCB do it.
I could send you some pictures so you get the idea if you want. It will show you the Top Bracket and Mounting plate and trackball ball as well so you can tell what these parts actually are. I do not have webspace to place them on the web, so if anyone wants some pics just request them via my email emailAddrRemoved This pictures would not be of my cabinet hack, but of the person's control panel who originally helped me. Although, my hack looks exactly like his.
PS: One good thing about using the HappControls Top Bracket and Mounting Plate was that they were cheap parts and if the trackball ever broke in the future, you could simply buy a trackball assembly from HappControls and stick in inside the Top Bracket and Mounting Plate you already have. I think the trackball ball from HappControls was the expensive for just a ball, but it was well worth it in my opinion. Still way cheaper than buying a completed trackball assembly, plus this gives you right/left mouse click buttons which you can attached via pushbuttons as well...
Hope this will help you out,
UncleT