IPAC 2 button wiring and MAME

[DaveC1964]

I have a small bartop arcade machine that I am wiring.  It has 4 buttons on the CP (I am not into fighting games so this is fine for me) as well as a stick on the left (which I know how to wire).  How should the buttons be wired so that most game's default settings will be correct?  For example Robotron would have these buttons correspond to the fire up, dn, left, right like a second stick would be as default, and the 1,2,3 buttons for missile command would correspond to either left button, up button,  and right button, or left button, down button, right button, etc as default, and Neo Geo games would map correctly as default.  I know I can configure each game in MAME but I am trying to pick a default layout that will work for most without having to plug in a keyboard and configure every single game.  I am assuming that most MAME games expect buttons in a certain location as default without having to change them.