Re: Vintage San Juan Photos

It appears there were 2 trains in those photos.
The first headed by 470 has an RPO followed by 2 baggage cars, and at least 2 coaches.
The second headed by 475 has 3 baggage cars followed by a RPO, then 2 more baggage cars, and then at least 2 coaches.
The reason for large number of baggage cars in the era, express freight has already been discussed.
In the photo William posted the train has 2 baggage cars followed by an RPO then 2 more baggage cars and 2 coaches.

Is there a reason that the RPO was placed in between baggage cars instead of behind the locomotive or just in front of the coaches?
At first I though it might be to separate the fast freight from the actual baggage, but with only 2 coaches I can't imagine that they would need more than one baggage care for passenger baggage.