Some progress. Interrupted the recommended route of construction to focus on the chassis to make sure it fits before progressing any further - esp to 5’3 clearances. Thankfully it all seems to roll ok. Am building 558 which had numerous changes to the norm - including no handrails on tank sides, or staff holders. This meant 6 holes to be filled in on tank sides alone….and you can just see on back of bunker where marking out is going on for the rear steps that 558 had, but few others.