Very good Simon!
As far as I remember the floorplates were fixed by countersinked screws, I am no100 % sure. Anyhow the plates were fixed, imagine the rattling produced by loose plates.
Tore
"countersinked screws" would match the style the Germans used to fixed the metal cover on the deck. I can imagine the rattling produced by loose plates
plus the noise of the plates jumping around while a depth charging would not be good
Also this morning I was able to work out the width of the floor in the forward part engine room from original German drawing
Tore can you remember roughly how big a single floor plate was. Were they all the same size or different sizes? I imagine they were small enough for a single person to remove them or did it take two people to remove them?