I did not see game title mentioned, but don't forget to research rom revions.
A few of the good folks have made free play roms. I think VP forums has them for a bunch of early Bally SS titles for download.

I had done double stack switch as well easy and clean.

Setting replay very low as well. Until 80b rom code just arrived.

I did a tiny momentary push button in the back of coin return chute so not obvious as well.

The big button is fine really anything that keeps you from having to open and close coin door is the way to go in my book.