Roberto listened - "Credo di si, I suppose. A tungsten alloy would be a strong solution, but thinking about the whole structure, well, maybe it's too much heavy, also talking about carrying it here. Niobium is lighter, but most importantly it's the best solution in terms of welding. I believe we can give a strong integrity with a good welding. I think niobium is enough. Well, if you have resources to spend, outer of tungsten and the internal weldings of niobium. Anyway, regarding the sector 4, well the sector 3 is already connected to the sector 2 above with large elevators capable of carrying bomber class, as you said before. So, if we are still talking about these classes, we can just extend the duct above, towards the sector 4, a bit of welding and it's done. If we are talking about larger stuff, I'd avoid to pass throught. Operations just from outside "