How many cruisers should have accompanied Force Z?

Should Force Z have had at least one cruiser for each capital ship?

That would be reasonable, with perhaps three cruisers if a carrier joined, although Force H had operated successfully with one cruiser, one capital ship, and one carrier.

Two cruisers would be a reasonable starting point for Force Z's two capital ships. Adding a carrier strengthens the case for a third. Force H provides a smaller working precedent: one capital ship, one carrier, and Sheffield. Its success qualifies the suggested ratio of cruisers to capital ships.