Hello Phil,
thanks for your kind words.
The Challengers currently available at our website were made for TRS2006. They require a new enginespec to properly run in TS2010-12, as well as some minor tweaking (the floating tender

).
I am testing the new enginespec on the Sherman Hill, and it works quite nice (but my spacebar is quickly wearing out

).
We plan to release them together with the updated FEFs, as a tribute for the 150 years of the Union Pacific Railroad.
We will also release the Clinchfield Challenger and the previously unreleased D&RGW version.