What I did:
1. Take front and side full body photos of yourself with your arms at a 45 degree angle
2. Crop the photos in a square, typically I use 10x10 in at 150 dpi
3. Import the two images as 'image planes' into whatever modeling program you prefer.
4. Build a very basic dummy using your proportions.
5. Go to an art store and pick up a pair of calipers for proportion measurements.
6. Use the calipers to measure the widest and most narrow areas of your body. (20 or so measurements work)
7. Wright or draw the measurements down for reference.
8. Set your grid size to use a dark grid line every 12 increments, and a lighter color for the lines in between.
9. Use a vertex to vertex distance tool to get the same measurements as the ones you documented.
10. Scale the base 3d model with the distance node until the measurement coincide with the ones you documented.
11. Import or build your armor.
12. Freeze transformations and delete history on the 3d object you are going to build.
13. Export the object as a wavefront .obj file.
14. Import into Pepakura designer.
15. Hit unfold button.
16. Change scale factor to manual and use a factor of 10 (Brings model to exact real world scale)
17. Unfold your model.
18. Print.
Good luck