I recently became aware of the relatively new Kadee "Whisker" couplers, which have a very fine phosphor bronze wire spring either side of the coupler pivot. These are much softer then the older sheet spring in the No.5 box and require much less force to couple. Kadee provide bulk packs of 25 pairs if you want to replace existing couplers.
However of greater interest to me was the new 156 "scale" head coupler "Whisker" coupler with long shank (25/64"), to replace the old No.16 coupler that I use on locos to reach over the front cowcatcher. The old No.16 only had a coil spring acting longitudinally, which did very little to keep the coupler centred. The "Whisker" coupler overcomes this problem nicely.
In conjunction, Kadee have produced a new short coupler box, No.252, to mount the whisker couplers in, which replaces the old No.16 box. The new box has a snap-on lid, which goes together in a split second. I always had trouble assembling the old No.16 box as the contact areas available for gluing were very small and they would often come apart. Some modellers melted them together with a quick touch of the soldering iron, but the new snap-together box is just brilliantly simple !!
The "scale" head couplers are a bit smaller then the standard heads, but couple satisfactorily with them.