Body mounted couplers also don't wirk well with truck mounted couplers. I had some time to work on the layout yeaterday and I put my "tourist" train made up of Riverossi and AHM passenger cars on the rails.
The train couldn't complete one lap around the layout without having a derailment of some sort. Due to their length, passenger cars will probably be more prone to problems than freight equipment, but many newer generation freight cars are also pretty long.
View attachment 53861 These are the Riverossi cars. This photo shows how far off center the coupler is when the car would be going through a curve. This offset tends to force one of the two cars off the track. The long coupler also can have a problem with coupler height. I purposely built in many grades. Some as steep as two and a half percent to as little as a half of a percent. I was very careful with these grades making sure that I had a good transition both on grades and curves. Watching the cars very carefully with the truck mounted couplers, it was easy to see that the coupler height did change somewhat as they passed from a grade to a level section of track.
I am extremely happy with my track work and after being in place for over 25 years I am having no problems with it. A couple of years ago, I had a 40 or so car train running when my wife called me up for some reason or another and I never went back in the train room until the next day. The train was still logging laps with no problems at all.
After pulling all of the Riverossi cars off the tracks, I put an eight car train of the Walthers North Coast Limited on the tracks (the train on the right) and let it run laps around the layout.
View attachment 53862
Ran it for around an hour while I was doing other things on the layour and not a single derailment.
The Riverossi cars are now on the workbench waiting to have the truck mounted couplers removed and body mounted couplers installed.