You won't need the upper track-mounting plate unless you desire to sand it down laboriously until it can somehow fit between the squished-in field plates. And even if you do make it fit, the mounting screws probably won't fit between the plates because during vice-squishing, the field plate divider has been somewhat mutilated and the holes squished. So, if you can improve on my methods, do so and let me know at my Email address, but for the best results with the least work, I recommend my way.
Assemble as Kadee directs, with the exception of the upper track mounting plate and the instructions which say to cut a short piece of track for the uncoupler (I just use regular flex track). And instead of cutting the gap in the center of the ties, you're best off simply removing all parts of all ties where the uncoupler will go. You can always add tie ends on the outside of the rails afterwards, for aesthetic reasons.
Assemble and bend the uncoupler (I use a vise and grip only the top 3/32" of the field plates of the upside-down uncoupler), making sure the little notch in the coil rim is exactly straight up before you sandwich the field plate divider between the plates.
The use of the lower track mounting plate, which I avoided in my last layout but included in the current layout, is important to its installation, but I used it differently than Kadee advises. In the last layout I discarded both upper and lower track mounting plates and made only a 5/8-inch by 2-inch subroadbed hole, and I used two wood blocks glued under the layout between which I wedged the foam-rubber-wrapped uncoupler assembly. I added silicone glue to fasten it to the subroadbed and track, and painted as needed so it looked okay. This was a slightly cumbersome arrangement, but worked fine. In the current layout I discarded the idea of positioning blocks glued underneath subroadbed—there's an easier way to hold everything precisely aligned which I'll get into later.
For each uncoupler I cut a 1 1/16" x 2 7/8" hole like the directions say—the lower part of the mounting plate fits into this with wiggle room.
Next you'll want to get the paint off the wire ends. Use a hobby knife in a fast whittling motion—away from you—with the wire against a table and the wire end pointed away from you, and the knife tilted towards the end of the wire rather than towards you, which would cause nicks and cuts in the wire. Solder good-sized wire (#18 to #24, depending upon the distance from the transformer) to these coil wire ends. The wire should be long enough to bridge the distance between the uncoupler transformer and your uncoupler coils, with a pushbutton in between. What transformer? If you're going to run the coils for over three seconds at a time, you may burn them out following my 24-volt method. But if you do three-second uncouples and are careful not to set things down on the buttons or wire carelessly so you end up with short circuits, then use a 2-amp, 24-volt AC transformer. After 3 seconds you'll begin to get serious heat-up, and eventually meltdown, at such currents and volts. On a previous layout, I used 5.75 mm field plates O.D. (instead of 6.2 mm) and 1-amp, 19-volt AC current and couplers bent as described above and everything works fine, but I think the sensitivity and fussiness of the uncoupling (I had to bend the trip pins just so) was cumbersome and the new current and measurement parameters are proving to be easier to work with.