I've never heard of a K-28 actually operating on the RGS, just that D&RGW had approved the track for them in the 1920's. Given the lower maint. stadards under the recievers after 1929, I expect by the time they were available, if they ever were (1941?) it would have been problematic to use them.
If K-28's were used at all on the RGS, I'd expect it would be on the North end where rail was generally heavier (56-60 lb with just a bit of 52 lb in places) than the South end with 40-52 lb rail. Most (not all) of the remaining 30 lb in later years was in sidings on the South end too. Of course stories told say that even Mudhens couldn't be used on the 30 lb stuff...
hank