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photoswest.org]
Check this link out--it is an excursion in which several cabeese were added to accomodate the amount of passengers. Now in normal operations on the D&RGW ng I have also seen video and pictures of the caboose directly behind the locomotive with no additional caboose at the end. A lot of these were on stock trains which may have been why the placement of the caboose was ahead of the train--must have been quite a smell to contend with. It may have also have happened due to lack of turning facilities or sidings or available sidings. I've seen some pic's of K-37's running in reverse Leaving Monarch which did indeed have a small yard. So to answer your question it is very likely that running a caboose just behind the locomotive on a normal freight was very possible--although it was not the norm. Hope this helps.
William
aka drgwk37