Rodney would narrow the target rather than trade broadsides

Would Rodney's low freeboard make her too vulnerable in a one-on-one fight with Bismarck?

No; Rodney would manoeuvre to present a narrow target, and her heavily armoured hull could absorb considerable punishment.

A realistic comparison cannot assume Rodney and Bismarck would steam side by side and exchange fire. Rodney would try to keep her bow toward the German ship, narrowing the target while bringing her unusual forward battery into action. Her low freeboard does not automatically translate into fatal hull damage because the exposed structure is still heavily protected. The answer demonstrates why tactical geometry, armour, and the way a ship presents itself matter as much as profile drawings or headline specifications.