edit 2: yea my mod should only block you from disconnecting the single train units from other wagons. From the mod portal description: There is no way to detach a single train unit from a larger train, it must be deconstructed. The disconnect wagon command will be effectively undone.
ah, yea so my mod does prevent you from disconnecting 2 normal cargo wagons in the same train as a single unit train, that isn't right. I need to make the detaching protection more precise somehow.
Far too many hours later I think this is fixed in the next release. Now the protection I need to stop a single train unit being broken up doesn't impede other carriage types in a shared train from being disconnected. The readme/mod portal description has been updated to clarify the new situation in the next release.
In terms of the coupler mod the single train unit is 3 parts. So you need to decouple -3 to drop the last single train unit from a train at a station. This seems to work on the next release now.
The single train unit will recouple itself if you try to break a single train unit in half.
