David.
I guess the removable deckrailing was not very much used on the frontline boats during WW2. The reason being they rattled a lot. We used the removable railing on work up, but usually removed the railing and stored same duly secured in the casing during patrols. Along the casingside there are holes about 30-35 mm dia. were you secured the round stanchions of about the same diameter having an eye on the top where you stretched a wire. Below are two images where you see the lay out. Indeed very simple but noisy.
Tore