Weight isn't going to be an issue, it's generally light for its size.
Flex; it isn't super soft or super stiff, medium flex is about where it's going to be.
Super model Alden and street rat Ryan talk about the 13/14 one here:
bitches love it when they can see my dick bulging against my outerwear. they are all like "is that a sandwhich for later?" and im all like "no, that is my massive penis sandwiched between the tight fabric of my pants and my inner thigh" - pomme-de-terre