It is indeed a milestone to see the chassis running on air, combined with much satisfaction and admiration!
However, the belief at that time that the "worst is done" flies in the face of experience.
My 2888 chassis (4-6-4) ran first on air in 1988 (hence the "88"). Finally steamed it with coal on a track at the Montreal Live Steamer's track on July 1. weekend 2009! For test purposes it had been steamed twice with a propane torch on a roller test bed.
My wife said she thought she'd never see the day.
Nice work!
Arminius