I started building in the meanwhile, and found out that this indeed a very lightweigth kit. Compared to other GP kits, were some balsa is of some really dubious quality and not very consistent, this kit has all the best light grade balse throughout!

I will however reinforce the fuselage sides above and below the wing, as there is only about 0.35" of balsa on either side, making is very weak at that point. There's no ply doublers, just balsa doublers, and I feel laminating some fiberglass in between them would make for a much stronger plane, while adding almost no weight...