To John Penca:
I went online and saw pictures of the actual C&O 2727 on display in St. Louis. A view showing the back of the tender lists the coal capacity at 30 tons and water capacity at 21,000 gallons. NKP and PM Berk tenders held 22 tons and 22,000 gallons so yes the tender would have to be larger to hold the extra 8 tons of coal. So, it appears that MTH is correct. The Alleghenies tenders held 25 tons and 25,000 gallons as per Al Staufer's C&O Power. Hope this helps.