It's difficult to comment on your setup, it's different to everything I would do. Are you really going for 4-locomative trains? Seems a bit overengineered. On the other hand, if it works for you, stick with it.
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Thanks for your detailed reply!

No, I don't use 4 locomotive trains, nor do I ...

Hello, forum! (first post)

I wanted to figure out my own method for a flexible refueling station (i.e. one that can handle multiple configurations of locomotives and cargo wagons without loading fuel into the wagons), but now that I've done so I'm ready to come here and have my design torn apart ...