New Memeber....

[modelsof1900]

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then the steam was piped to the front engine, superheated again, and used in the larger, low pressure, cylinders, before being exhausted.
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Dave

Dave, all correct that you have written - with one exception.
Steam was generally not superheated on its way from back to front cylinders. There was only a very seldom realized that steam has got a "rewarming" (lesser superheating) at a few engines, which was more prototypes and trials for more powerfull engines. The Santa Fe did make such trials with its mallets with articulated boilers and their 2-10-10-2 class 3000.

An addition:
It is not a technical problem that cylinders of a mallet engine equipped with piston valves working together with cylinders working with slide valves. It it would be of interest I could give a few more explanations.
This problem will be solved by small differences at the valve gear, which you can see also at your picture of Old Moude. Look for differences at combination levers. A second difference is not visible - the rear eccentric crank is positioned a small bit in forward direction and the front crank is standing a bit to rear - in both cases that the main cranks are standing in most lower position.

And last,
EM-1_7600, a very good idea to build this very early mallet engine in USA. Wish you success!