Hi Filippo,
The problem is that very few (almost none) of the 1000s of U-boat photos show this area. It could be that there were variations in the floor pattern between boats. This is likely given the known variations in other ways to the hundreds of VIICs. But we don't know as we don't have lots of photos to compare boats.
Luckily for you this video shows U 552, the boat you are building. So you know for 100% sure that what you see in the video is correct for your boat.
If Siara had seen this video he would have gone with the pattern you see.
Note that U 564 (another Blohm & Voss boat) had the same pattern.
Cheers,
Dougie