a standard x-arcade 2 player unit is pretty narrow, it's been a while since i looked at mine, but i can't imagine you would be able to fit a trackball in there. From your comments, i take it you have a cabinet that you mounted an x-arcade stick to, is that correct? why not build your own panel? even if you are stuck with the same dimensions as the x-arcade, you could no doubt tweak the button layout to something a little more suitable, along with space for your trackball. you could transplant the x-arcade components into your own panel so you wouldn't have to buy anything else.