Hello, Fitzsimmons,
I understand your problem: updating the engine files of our steam locomotives to TS2009/2010/12 standards is driving me crazy. I have spent countless hours trying to fix them by trial and error. Unfortunately, the procedure to make a decent steam enginespec seems to be the best kept secret of Trainz

.
I made some progress using Billegulla's spreadsheets: both the FEF and the Challenger now work more or less as intended, but still need some fine-tuning. I hope to release the updated versions soon.