So the Kinematic couplers... They simply don't work under the weight of a long train as the mechanism binds and causes derailments. Even if nothing derails they cause excess forces as the distance between the cars changes on curves. You can even hear the remaining train accelerating and decelerating behind each coupler set.
I'm not a fan of the #1 scale Kadee coupler solution... The swing limits the functionality of the cars. Meaning you can't couple an auto rack to a short fixed shank coupler on a gondola car.
The solution I came up with (along with AcelaNYP's help) was to mill a brass plate to fixture a Lionel coupler to the body of the car. It uses the existing mounting holes so the car doesn't need to be modified in any way. My only complaint right now is there's no uncoupling tab for use with uncoupling track.
These auto racks can now be at the front of a 30 car train with no problems on O-72 track. The coupler also springs back to center every time. Distance between the cars isn't much greater than stock. And these cars can be coupled to anything.
I'm honestly a bit stuck with the uncoupling tab problem. Would love some input!
If anyone is interested I'm happy to upload a STEP file of the part so you can make these too. I'm sure I'm not the only one who was unhappy with the stock couplers.
The green ones have been converted and the yellow ones haven't. For comparison:
