If you look through my Pace Car thread, I had to cut holes for my power windows. There is a dimple already there showing where to start. I think I posted some pics.
I also noticed that the original power window rubber hole grommet (on the wiring harness) was shrunk smaller than the original hole on my old doors.
So, you have to cut a hole just large enough to hold in the grommet at it's locking groove and not the size someone here will measure and tell you to use.