Hi FokkerFodder,
not quite, the basis is the "ENGRAVED BRICKWORK for Das Dock" kit from Uschi. Since the actual dry dock was too expensive for me, I bought the update for the dock. I then drew the supporting structure with Inkscape and laser cut it. Uschi's ENGRAVED BRICKWORK is for my U-9. For the UB-10, I copied two segments of it, laser cut them, and then clad the walls with basalt stones from the railroad accessories. The large granite slabs were printed on paper and glued onto the paths.
cheers
Jürgen