Its not putting the Kadees on....thats the easy part.
Maintaining the close coupling on the curves without derailing is the issue, because of the diaphrams. They are pretty rigid, and when they go through the curves, the edges of the diaphrams catch on one another. The Kadees do not allow for as much side to side swing also adding to the derailing issue in the curves.
The cars out of the box are pretry close coupled already. I'm definitely not one to vote against Kadee conversions, but I've done it. Unless you run in a giant loop with no S curves or using cross overs....its not worth my frustration. I do NOT want to be limited to where I can run the cars.
