Hello
DiegerfonGD
I'm just finding this thread, but I think I have some information that you may find useful.
First, Brad from Impact Props makes his foam suits entirely from scratch. He determines the sizing of the armour pieces and all of the details by looking at reference pictures and eyeballing approximately where those same armour pieces and details would be if he were to wear the armour. While this is a completely valid way to craft the armour, there is not much anyone can say to really help you develop this crafting method besides saying practice makes perfect. Building things from scratch really is lots and lots of trial and error. Brad has been making foam armour for a long time and he has a very good eye for making it up as he goes along, but I can't imagine making my suit of armour like that.
Most foam crafters follow a template like the one you've linked. This is the method I would recommend for foam crafting because there is a lot less guess work involved. You will still have to read between the lines sometimes and fill in some gaps yourself, but the template will do most of the heavy lifting for you. You will still need to figure out what size you need to scale the template to however. Many folks have mentioned Armorsmith, which is what I used for my most recent suit. If you're not keep on using the program because of it's apparent lack of support currently, you can still get a pretty good idea of how big to print the templates by measuring the space it will take up over your body and scaling appropriately in Pepakura. There is a nice tutorial for this that I will link here:
Hi everyone, Though I haven't been a member here long, I’ve already seen several new threads pop up with noobs asking how to scale their armor pieces. Sometimes, they have already read the other scaling tutorials, and still have trouble. So, I thought I’d share my method for scaling that I...
www.405th.com
Even with the best tools and accurate measuring the final size of your armour is ultimately just your best guess. There is not really an exact science to figuring out the scale. Your main goal is that is
looks like it's the right size, not that is actually is. Even with a template you may find that you need to do some trial and error. I had to remake a few of my armour pieces because I scaled them a bit too large/small. It's all part of the crafting process.
Best of luck on your build!