Hi Santi_Cavallo,
Key is to keep things light and current consumption low. Try to build an airplane that consume half or less of your available solar power, and then fly it with battery for an hour or more. Then you are ready to install solar cells. You can remove the case of GV5 and GV10 also remove terminal screws and solder cables directly on PCB to reduce weight. But you are right that GV10 are heavier that were why I decided to go with GV5 . I would also use NCR18650GA or similar cells instead of lipo to keep weight down. I started as a noob and it took me three years of spare time to build, test, fail, improve, and then repeat many times to succeed with my solar airplane. Good luck with your endeavor!