Thank you very much Cedro,
Sorry, it´s my fault, the glassfibre is a shell of 2 mm of thickness in the OUTER ceiling, in the inner ceiling there is a curved shell of plywood of 6 mm of thickness. The glassfibre curved shells are divided in 2 parts of 1.5 m and 1 m length and about 12,5 m of curvature. Both of them are about 2 m wide; they are some kind of stiffners for the ceiling main structure. I don´t know what kind of glassfiber (or plywood)is, I´ll have to choose the most suitable for my model.