The two I was thinking of were South end shots, one between Mancos and Brayton and the other at Glencoe. But the common practice on the South end was to run the helpers on the rear or cut in. The RGS did what would be politically incorrect today by running their little engine helpers behind the caboose. But photographic evidence would seem to indicate that with the K-27's running as helpers they would be cut into the train.
Bottom line is that the RGS, like any practical business venture, ran things in the most efficient way for their unique operations. It was easiest to cut in or cut out a helper when it was behind the caboose. But we fans find it too easy to look at a couple of photos and then say "they always or never did IT this way," whatever "IT" is.
"Perhaps" and "As far as I can tell" work much better than "never" or "always."