I have a set of Athearn streamlined passenger cars. And I have 2 heavyweight cars (RPO and baggage). Currently, I'm considering using the heavyweight cars with the streamlined ones. I've seen some pictures of mixing heavyweight and streamlined passenger cars of model railroads depicting the 50's. I've been informed before that this kind of mix did happen in real life, but that was long ago and I'm not sure about this since I haven't seen real pictures of passenger trains with this mix. BTW, my passenger train is a 1950's Santa Fe with a F7A and streamlined passenger cars. I just want to know if passenger trains then did mix streamlined and heavyweight cars, regardless of road name. But I'm also interested if Santa Fe did practice this too.