Novice experience with Kadee couplings

Kadee do couplers with underset or overset shanks as well as the standard ones.

This is not the relevant dimension. Is the coupler head at the correct height? If so, bend the uncoupling pin up slightly to so that it clears the magnet. Kadee sells a tool for this, but I've found a beading pliers with stepped and concave jaws works just as well, and is cheaper. Available at craft/jewellery supply stores.
Again, the coupler head height governs, not the uncoupling pin. If the head is at the correct height, bend the pin down until it just clears the magnet.
The problem will be with the wagons. As with all couplers, the coupler heads on all rolling stock must be at the standard height. Use a #206 gauge for this. It's plastic, so you can use it anywhere without risking a short circuit.
Go to for tables showing what's available.
A) Essential (that's why I'm repeating this advice ;-)): Coupler head height _must_ be set to standard. Get a #206 coupler height gauge. This will gauge the coupler to the correct height. It also gauges the floor of the wagon, so you can determine how much if any plastic shims (packing) you need to mount the coupler correctly. IIRC, NEM and NMRA coupler heights are the same, but if not, you can allow for that when you use the gauge. The gauge also shows whether the uncoupling pin is too high or too low.
B) To raise the coupler head height: Use "underset" couplers, ie, ones whose shank is set even with the bottom of the coupler head. This will usually bring the coupler head up to standard height. Kadee does not offer these with NEM shanks, so you will either have to use a "talgo adapter", or mount a whisker or standard coupler on the wagon floor, using #232 coupler boxes (gear). Sometimes, coupler boxes on the rolling stock have removable covers, ypou often use these as is.
C) To lower the coupler head height: c1) Use "overset" couplers. c2) use plasttic shims bewteen the coupler box and the floor.
If your curves allow it (1), mount all couplers on the wagon floor, never on the bogies. It's a bit more work, what with bogie-mounted couplers pretty well standard for UK/EU stock, but it's worth it. You may have to cut a bit of the buffer beam or add plastic shims (packing) behind it to get the coupler head at the correct height.
HTH Wolf K.

In message , Wolf K writes I've got a #205 height gauge (it's part of the starter kit). That is what I was using to judge the height with (rather than just going by eye).
Without checking, I suspect that most of my rolling stock will not have NEM sockets, four wheeled wagons will be on the body anyway, not so sure about the bogie stock. Locos (which will probably be new) will be on NEM sockets, not sure how easy they will be to fit gear boxes to.
Yes it has, thanks.
Adrian

[...] Good, I have one of those too, mounted on the end of a piece of straight track fastened to an 18" long board. This lives on the workbench for checking couplers. I also have the 206 because it's plastic, so can be used anywhere on the layout as needed without risk of causing a short circuit.
[...] I have had to adapt KD coupler mounts to all kinds of situations. It sometimes takes a bit of doing. But it's a "learning experience", which the healthy-brain gurus say is good for the neurons, so enjoy it while you can ;-)
You're welcome. Wolf K.

Number 16's are my choice for most stock without NEM pockets, can be tricky to put together, springs jumping all over the place.