Growing concerns about the environmental impact of aviation have (re)sparked interest in hydrogen aircraft as a greener alternative. However, using hydrogen as fuel introduces technological challenges, particularly with regard to on-board storage. Integral tanks, which are part of the aircraft's main structure, seem promising but existing designs show limitations in their integration with the airframe and insulation capabilities. To address these issues, this study proposes a new integral tank concept featuring a double wall architecture with vacuum insulation and outward facing structural reinforcements connecting to the fuselage skin. A parametric sizing method based on finite element analysis is developed to assess the mass of a tank employing this concept and its sensitivities to design choices. Preliminary results point to fuel containment efficiencies consistent with previous designs, with buckling stability identified as the critical design criterion. These findings provide the basis for further research and could be complemented by integrating the developed framework into a complete aircraft design tool.