Just noticed this... but for argument sake, Walmart sell these mats as well, you need to look in the section where the weights and exercise equipment is. Found it next to yoga mats in my local walmart. This is the same method I did the ODST gaunlets a year ago.
Great scratch build... can't wait to see it painted.
Pete used this method as well when making the Animatronic Halo Wars Elite armor plates... if you are a cardboard builder, this would come rather Natural to you I should say.