Definitely not asking too much - sometimes Pepakura to foam adaptation can be tricky. I'll give you some basic pointers to start:
1. Take into consideration the thickness of foam. With pepakura, you'll be folding over sides that may only be a few mm thick. When working with foam, you don't need those paper sides of pepakura, as the actual foam thickness will make up for it.
2. Figuring out bevels is always difficult. For sharp angles (as opposed to curves), one trick, which is a little untidy behind the scenes but still works, it to cut both edges on a 45 degree angle, glue the tips of the edges that are seen and then on the back, use hot glue to fill in any voids and position the edge to the angle you want while it cools. That way the seam is neat, the angle looks good and there's hot glue keeping it together.
3. Don't worry about the little details. With high-detailed pepakura templates, they may require you to make tiny little details, or grooves in surfaces. But you can make those details out of different thicknesses of foam, and grooves can be burnt (with a soldiering iron/wood burner) or scored and heated to open up. If you have two edges of foam that come together and there's a groove where the two meet, you can sand down the tips of each edge to get that depth.
4. If you own Pepakura Designer or Armorsmith, you'll be able to take 3D models or existing Pepakure files and modify them to suit foam better. Heck, you can even do it in Blender with a 3D file of the armour!
5. It may be better to use the low-poly pepakura files of armour for foam, as they don't have as many details. This means you can form the basic shape first and add details later.
6. To align pieces, use what's called "registration marks" - notches or lines on two sides of where an edge comes together that tells you how to line up a piece. When getting ready to transform the printed pepakura patterns to foam patterns, draw a line over the seams onto both pieces that'll split. This line is your registration mark.
Sorry if I'm rushing it, if you have any questions just carve out a summoning circle and chant my name. Or, I guess, just reply, that'll work too.
