The indvidual buttons should be as close as possible.... On a real arcade machine (6 button of course) they are VERY close together. A common newb mistake i always see are button holes that are too far apart..... When the buttons are installed there should be about 1/16-1/8 space between the lips of the two buttons. And 1/8th is really pushing it.... it should be closer to 1/16th.... If you make them further apart it will still be playable, but it will "look wierd." and a neogeo span of 4 buttons is going to be hard to reach.