I use player 1 start and player 2 start as the mouse buttons. Dedicated mouse buttons are generally seen as a sign that you are doing it wrong.
That sounds like a good idea. But I do believe your? or "That" stance is way too harsh an attitude to have.
Maybe you want to have your mouse buttons closer to the actual ball... rather than reaching up deep into the panel, for example...
There may be other alternative reasons too. Thats all that came from a brief moment of consideration.
At the end of the day.. its Your cabinet. Do what works best for you, and what makes you happy.