start button as coin button....
I guess this doesn't really matter what encoder you use, (or I use gamepad hack...) but more a mame config question...
I have not played a lot of games in mame...
but most newer games will work fine....
(when you start a game.... like ms pacman... you press the button once, and it'll give you a credit... and then you press it again, and it'll start the game, and at the same time give you another credit....)
for some older games... (I don't have much time to try all the older games.... a lot of catching up to do... haaa haa..) some of them will NOT work... they'll need another button... as to how many.... I really donno.... but try it... I think you'll find it acceptable... (I think so far, I found less than 10 games... I can live with that....)

ohhh... ps: yes, for guantlet... since the start button is also the potion button... so.. everytime you put in health... you'll also use 1 potion or something....