I know this has been posted before by another member but I thought I would post my experience.
It all started when I read I needed to by a "Dremmel" in order to increase the slots slightly to allow the slightly bigger than quarter tokens to pass through the hole.
I went off to Bunnings (a major hardware chain here in Australia) to hunt for a "Dremmel" tool. I found they were $90, I couldnt justify spending that sort of money on a tool ill only use a couple of times. So I worked out it was nothing more than a really cool engraver, so I purchased a "EL CHEAPO" $12.99 mini hobby kit and engraver.
Charged it up and started using it and within 20 seconds I could fit the tokens through.
What you do is basically engrave away the metal on the sides of the coin slot, very small amount at a time and keep checking to see if the token can fit through.
Until you can drop the token through no problems!
And finally get some modified mechs from ArcadeNerd or .984" token mechs from Happ.