Why a larger Nelson class could trade armour for speed

Would a larger class of Nelson-type battleships have been faster than the historical pair?

Probably. With eight ships rather than two, Britain could accept somewhat less armour and aim for roughly 28 knots.

Building only two Nelsons encouraged the Royal Navy to maximize armour and firepower, even at the cost of speed. A class of eight changes that calculation because the fleet can accept slightly less protection on each hull while retaining considerable strength in numbers. In this counterfactual, the result is a Nelson-type battleship capable of roughly 28 knots while keeping its 16-inch guns. The larger programme could also reinforce continued use of 16-inch armament in the next treaty generation. A pair of slow, heavily protected ships and a numerous fast class solve different operational problems.