Ok... I just got my 3" Betson Imperial. 
I ripped open a mouse I had laying around at work. Its a nice IBM mouse without the wheel. 
Soon I will do the soldering to hack it. 
But I have a question. I should know the answer but would like to know. Why must I solder the wires to the mouse board? The trackball has the wires from each board on the trackball (x and y) Why can I not just hook up the mouse wires to the wires that come out of the trackball. 
Please forgive me stupidity...