Nice model Bill.
I've got the C-21 (CF&I 101-102) erecting card, the C-25 (CRRR 103) erecting card which has some relevant information for both classes, the folio sheet, and lots of photos online and from the Crystal River book and Narrow Gauge Pictorial 11. Also got some photos and AFEs from the CRRM. Also, according to their catalog, Precision Scale Models has a C-21 cab detail drawing available, will be ordering that, probably part of a larger set they had done for a brass production run.
Also in the Maxwell collection are two drawings – D-137 and D-137t (plan view of tender) – probably as the C-21s appeared towards the end, drawn by Maxwell about 5 years after the engines were scrapped (1950-51). These I don't have and currently can't get of course, would probably help a lot, especially the tender drawing. Whaddaya gonna do?
Still, lots of unknowns.
Mike