I rebuilt the superstructure (it is level, *not* sloped
as the drawings suggest).
I build a new and smaller periscope housing, different from the drawings too.
and a toy-tank-hatch made a perfect sub hatch.
made a mold of plaster, put in a bit of grease, and
filled it with polyester filler. presto : two hatches.
and the sanding of the hull continues of course...