jusqu’à means "up until". Mass is that; mass, so 350 kg empty, no batteries. Interlingual issues can easily obscure those kind of things, especially from the French ;-) Nice project, but is it more as a nice cad-drawing and some numbers? As for the 18m tips, any reason to go specifically for that span? From my view more is better (I'm religious about TINSFOS..), was that the practical span limit for wing loads and rudder effectiveness? A true TMG with gliding performance good enough for "real" gliding (say, a polar that's as good as a Libelle/LS1 with ballast) must be the holy grail for many clubs.