Point is, the CG is the important point, not that you have to add weight to get it there. While it is true that lighter flies better, you are very light to begin with, the added weight won't make a real difference. The 60 size flies great, you will just add to the stability of it in the wind. Try and make sure that the wing is in the wing saddle correctly, and that you are measuring close to the fuselage, about 1/4 " out from it at the saddle. And you will end up slightly nose down when you are finished. A little nose heavy may make you land a little fast, but tail heavy won't fly at all. Good luck, you have a fantastic trainer that will take you a long way. I have 2 of the 40 size that are going on 6 or 7 years old.