I will tell ya that right now, you will want AT LEAST 2 packs of foam as long as everything is scaled just right. With the foam being as thick as it is, you need to scale things a little bigger. If you don't plan on wearing anything bulky under your armor, then just measure yourself and add 2 inches to that measurement. This will at least ensure that the foam isn't too tight and decreases the possibility of your foam armor falling apart and constricting your movement. If you DO plan on wearing something thick for your underarmor, then measure yourself WEARING the intended underarmor. That will help get a more accurate measurement.
That concludes pointer #1.
When working with the foam, you will want LOTS of hot glue. And I mean LOTS!!!! You will want to use some glue to glue 2 pieces together and once that is dry, you will want to go over the seam on the INSIDE and lay down some more glue. Trust me on that one. While the hot glue holds the foam together like a champ, you will want the added strength of keeping it together when wearing it so make sure you really cover the seam good with blobs of hot glue. XD If any hot glue comes out and shows on the outside of the piece, wait for it to dry and using a VERY sharp blade, carefully cut it off to keep it flush with the top of the piece. Do NOT try and use sandpaper to sand it off. I had an idea and thought it would work and failed miserably. So try to not get a whole lot of glue to come out the top. If a little bit comes out, you will be fine. Just use the tip I gave.
Now, when creating your templates in pepakura for the foam, you will want to remove the tabs on the pieces in pepakura. You DO NOT need these for the foam. In order to do that, in pepakura, click on 2D Menu and then click on "show flaps". This will remove the check mark and if you look at the pieces to the right, they no longer have the glue tabs. Once you have it scaled and the pieces arranged on the pages for printing, you will want to create BIGGER templates than the ones you printed out, IF you want. Some people do and some people don't. I myself made the templates bigger by taping together some pieces and then tracing it onto the foam. Bigger pieces seem a little easier to work with.
Those pointers should help you get started.
