Only thing is, this route will make it so that it isn't shaped for you. I would go the route of something more similar to making a dress form and then use that as the base. Otherwise this could be rather uncomfortable if not made to fit your body.
Foam utility belt tutorial Where the heck was this when I needed it for Super Ariel?
Let's make your own Iron man suit
Pepakura - print out 3D paper models. Made Iron man mask.
Armor tutorial (this is VERY detailed!) using HDPE (High Density Polyethylene - the same stuff cutting boards are made from!) - highly cost effective, safe, durable! I LOVE this post!!!