The baggage cars ahead of the RPO were used to handle the LCL shipments. These shipments were separated from the Railway Express and baggage shipments that were in the baggage cars between the RPO and the coaches.
The ultimate image of the San Juan during its heyday of moving LCL (and probably making a bit of a profit) is this shot taken by Richard Jackson of eastbound # 116 thundering up Cumbres just up grade from Coxo Crossing in July, 1937. I fell in love with this shot the moment I saw in my new copy of Narrow Gauge In the Rockies I got for Christmas in 1967...
I was so enamored with the shot I had the late Jim Finnell reproduce it in watercolor...