Warrior's historical achievement came from combining technologies already regarded as proven, and the same combination could be attempted in a two-decker. The preferred starting point here is the Duncan design, regarded as a better steam ship of the line than the Bulwarks. Doubts about the Bulwarks while they were still on the stocks help explain the Admiralty's willingness to cut them down. The Duncans provided a nearly 6,000-ton, 101-gun starting point with about 3,490 indicated horsepower. Adding armor and enlarging that design suggests a ship of perhaps 12,000 to 13,000 tons. This is a tentative scale estimate for the counterfactual, rather than a completed design.
Notable Point · 36:12-38:12
Why Duncan supplies the proposed armored two-decker's starting point
A Duncan-based design could combine Warrior's technologies with a steam two-decker hull, reaching an estimated 12,000 to 13,000 tons after enlargement and armor.