I hate to break it to you, but you probably will not find anyone to help you out with this. There will be plenty of people willing to help if you want to make your armor the more conventional way, but most people here think that making metal spartan armor (or any "real" halo armor for that matter) is a waste of money and time. The armor we make here is primarily for costume and display.
That being said, if you change your mind and decide to go the pep/foam/sculpt route, I am confident you will receive plenty of advice and help. We here at the 405th see far too many new people coming to the site with aspirations of making "functional" armor (I've even seen someone recently make a bulletproof ODST chest, but this project was going to cost upwards of $5000). These projects always fail (at least I've never seen one to completion). So, save your money and sanity, I beg you.