I use the Kadee 745's since the boxes are plastic and have some give to them. I add a MicroMark shim and walk the screws in. On the occasionally stubborn car, I enlarge the center hole in the Kadee box slightly (3/32" as I recall) and it mounts. I use the 2mmx8mm screws from Micro Fasteners.
My New Year's resolution is to get all of my early Atlas hopper acquisitions converted from the hi-rail couplers to Kadees and eventually to 2-rail. There are a lot of them, plus five Lionel PS4427's that I have to switch over.