The pepakura files would give you the sizes you need, but putting Worbla over it could mean losing the smaller details... but I'm a trial and error person myself, so you may want to try!
Here's the album my husband made of his Cap armour, which shows the progress from paper templates to Worbla shaped over his chest/back, to the foam layer he made for the scales, and the layer over that. Let me know if you have any other questions about it! There are some good youtube tutorials covering this method too. 
