Your overall design is solid, but needs a few additions. Things like building up the fore-arms and legs can go a long way in the process of making one of these suits. Also keep in mind that unless the guy you are dressing up is 6'10" and has the build of a small rhinoceros... it's not going to fill out exactly, now that's not to say you can't make your son look amazing, as he already does. If you need any help or sizing let me know. Also we (my airsoft team) have begun the process of building the Mark 2 Juggernaut from Modern Warfare 3, so if we come across any helpful tips or tricks when constructing this suit, we will let you know. Good luck!