I've just uploaded an invisable coach with no size or passenger carrying quantity for use as a coupling converter so automatic and chain stock can be easily added together in AE to make train formations. I've included vac and air versions. The only drawback is if you use in a drivable train between the loco and stock, if you uncouple from the train you will not be able to re couple again. I've put it in the non passenger subsection of the passenger coach section.
Jim