JUST EXCELLENT!!
Comparing British engines with US designs, the US designs always have "longer boilers"... but that may be an optical illusion if they are smaller diameter... I assume possibly because the fuel, being wood in the US, needs a much larger grate and firebox? (This was the reason for the US designed 4-4-0 locos having such a large firebox). And possibly larger flues to avoid soot build up from the wood resins? hence the flues need to be longer to be more efficient at capturing the heat? Coal being a relatively cheap fuel and readily available in the UK around the era when British Makers were making these engines, probably meant the flues tubes were smaller and got their efficiency that way and boilers were shorter as a result? Does anyone know the whys and wherefores?
K2