OK, this is getting kind of weird. About the compressed air: When the project began, we just had 300 feet of track at the fairgrounds. Demonstrating the engine to schoolkids, etc on steam would be a huge amount of labor, while running a short distance on air would accomplish the purpose while saving 1472 days, allowing full steam operations during guest appearances on other railroads. Time has marched on, though, and now we are in a totally new location with a 1/2 mile loop track for demonstrations over any distance. The compressed air will still be useful for moving the engine short distances, but the plan is for full steam operations. There is no nearby source of coal (nearest is more than 100 miles away), so the decision was made at the beginning to fuel the boiler with diesel - don't ask me which type, that's not my area of expertise. Fire danger in pur area in recent years has proven the wisdom of this choice, with the D&S converting to oil burners. So yes, the compressed air system will still be there for limited use (it was designed in at the beginning with compressors hidden in the tender), but the main power will be steam, oil-fired. End of story.
The end product will be much, much closer to the original than many people think. Keep the faith, it's coming.