15 for arms, 20 for legs. The 25 for the backs of the legs is a last case scenario, if you after 20's you cannot get your leg's into the pieces.
Dont think it matters of which method for velcro, as you said as long as they open to the inside. I started out with velcro shins, but you could really see the openings still. I then went hook and loop and did some heat bending with a heat gun and LOVE them! I really dont need the hook and loops now even, after the heat bending and shaping, they pretty much close up on their own without anything with no gap at all. Something more to think about!