Would mixed boiler batches be too risky?

Could the first four ships split between small-tube and conventional boilers to compare the technologies?

Probably not: the Navy would likely judge the cruiser trial acceptable across the class, since the ships remain useful station vessels even if they miss their ideal speed.

The Royal Navy would probably accept the new machinery across the class instead of splitting the batch into a formal comparison. The service already understands conventional boilers, so another control ship would add little. Missing the full 28-knot target would also be less damaging in a station cruiser than in a battleship. The class offers a lower-risk place to gain operational confidence with small-tube boilers while retaining useful ships if the experiment underperforms.