Evidently, the design and construction of the Sheepscot engine house will be the subject of keen attention!
I am attaching a diagram of an engine house design that includes an excellent form of smoke jack. Provision for good ventilation around the hot uptake is shown.
Looking at the photograph of the Wiscasset maintenance facilities that appears on page 221 of Two Foot to Tidewater, it can be seen that a rather more simple form of smoke jack was installed, there.
Given the existence of the fire safety issue, there will be a need for good judgement in the formulation of a smoke jack design for Sheepscot.