My guess is that after seeing your pix that the "road" to Whiplash is going to get a lot of use.
As I remember the various turn offs and looking at my topo map, you go past the 305 curve, through a cattle guard, over a small hill, and then turn left to get to Big Horn (if you come to the railroad xing, you have gone too far).
It has been a few years since I have done it, but in the 90's you could drive a normal car to Big Horn so long as you were careful. Indeed I took a Ford Taurus off road to get out to the end of one of those long ridges that the railroad loops around. But beyond Big Horn the road deteriorates big time. It was rough even with a 4x4 (and I didn't go as far as you went).
But your afternoon pix at Whiplash really are nice.
As spectacular as the climb from Chama to Cumbres is, the east end of the railroad has more "charm" for me. Early morning and late afternoon lighting really bring out its wild west beauties. It is too bad that photo charters don't pay more attention to the more creative possibilities there, some of which your picture show very well.
We definitely need another moonlight freight out of Antonito!
JBWX