this is a personal preference but you only need 1 admin button.
make make controls admin_button+something else..
example instead of having a button just to drop coins why not do this:
admin+1p joy stick down = coin drop 1
admin+2p joy stick down = coin drop 2
admin+1p joy stick left or right = pause
admin+1p start+2p start = exit
i'd also add a way to get into mames menu for input/dip switch control..
perhaps admin+1p joy stick up = mame on screen menu.
again this is personal preference, but this way you save cp space, time making holes, and money buying buttons.
a word about the mame menu though others will be able to get into it and mess with your settings.. so you may instead want to put it as a dedicated button accessed though the coin door.
2. move the start button, perhaps as high up as possible but inline with the first row of buttons.
Like my picture above.
ya.