Sumpter Valley stacks and tenders

Thank you for that information, Bruce. As Earl pointed out, tapered stacks would certainly complicate the mounting of an external Rushton stack enclosure.
Your message suggests that the tenders shipped to the WP&Y with Alco Mikados 19 and 20 were originally paired with SV Baldwin Mikado No. 18 and Baldwin ten-wheeler No. 50. That is at odds with what I understand to be true, and I hope there may be a way to resolve the difference.
The records kept by Earl Emlaw, Chief Engineer during SV's final years, show that the tenders shipped to the WP&Y in 1941 with Alco Mikados 19 and 20 were originally the tenders for Baldwin Mikados 16 and 18, and that SV's Baldwin ten-wheeler No. 50 was sold in 1944, with its original tender, to Dulien Steel Products of Chicago, Illinois, for delivery to the government of Peru.
Mr. Emlaw's records show that the original tenders for Baldwin locos 16, 18, and 50 were very similar, with light weights of 31,511 pounds each and water capacities of 4,000 gallons each. The only difference he shows is in the capacities of the fuel compartments, with the tenders for locos 16 and 18 rated at 6.5 cords of wood and the tender for No. 50 rated at 6 cords.
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Thanks to all who have pitched in on this topic. Your research and discussion have fitted some new and interesting pieces into the SV locomotive history puzzle while opening up new areas of inquiry.