Consider putting on the Oscar restricting plates... They are about the same price as 4way joystick, and you can remove them to play 8way games when you want/need.
In a cocktail table you are really limited to space... so you don't usually have the option for both... thats when I really think the plates are amazing.
And your right. playing 4way games on a 8way joystick suck. I would rather play pengo with a keyboard then an 8way