Dave, I can't say this without sounding like I'm critical. I just hate reading some stories posted of jamming some other screws in there! I realize you used a tap, but why?
I use 2m x 8 metric screws and don't tap anything. I think once you get an assortment of them, you won't be shy at going to the metric screws first before the tap.
I just converted an Atlas tank car from the old stock broken couplers to KDs. I used 2m x10 to allow for the shim.
I like to have metric stuff on hand when needed. I know many here, resist using and/or keeping the factory threads for some reason beyond me.
Tom, I too wondered why MTH chose to put the tether system down there in plain sight? It is a hassle to connect. It is hidden on the MTH G scale stuff inside the door diaphragms.
look at page #9