To Chuckt and Rick:
The glassing overhead was not really difficult, after preparing each strip of glass, positioning it well, impregnating the wood first, then a second coat for the impregnation of the cloth, which then stuck on the hull without more difficulties than on the topsides.
There is, of course, a rebate that has been cut (about 1mm. deep and 10 cm. wide) so that each strip of glass overlaps the previous one, thus create a "structural continuity" of this sheathing, although this structural integrity only concerns itself, not really the hull whose rigidity is immense when compared to this "cigarette paper" thin sheathing (well: > 600 g/m2 still!).