I just recently purchased a cabinet.. and, I'm sacrificing a little bit of 'looks' in order to add a Control Panel that is big enough to handle the trackball. It's VERY important to me.
Not only are there great games that use the trackball.. Marble Madness, Centipede, Blades of Steal.. but, it also makes moving around in windows a heck of a lot easier.
I'd do it, if I were you. A couple of inches more won't make a difference.. unless you really do live in the smallest of all apartments.
david