Re: counter balances and speed.

Chris:
You have to keep in mind that the San Juan stopped at LaJara for mail, express, and passengers. Probably took on water as well.
Some of the old timer Rocky Mountain RR club photographers tell stories of Rocky Club trips running at over 50 mph between Antonito and Alamosa. John Maxwell was once stopped by the Highway Patrol just trying to chase a Rocky Club trip.
Another thing to keep in mind, the track was better maintained during the 30s and 40s than in the 50s and 60s. Look at some of the movies of the Shavano running out of Salida in the late 30s with 479. Her drivers and running gear were a blur.
A 470 was probably the best of the Ks for speed, after all, the crews called them "sport models."