Thanks guys, my son had a great time being a grunt, and this costume was well received! He was the best prop I could have.
Although is it bad when the prop receives more attention? LOL. He was really tired by the end of it though, and got to the point where he audibly groaned when someone asked for a photo. He loved seeing the other UNSC folk though, and loved having all of that attention on him...... poor grunt.
I did find out a few things to do to fix this costume though. Seriously need to reinforce the openings to help avoid cracking when this is being put on and taking off. Also the model magic isn't the strongest modeling material for this application, so if any one uses it, coat any areas that would receive a lot of chipping with a great deal of resin. His toes got beat up in an awful way, so his toes looked like they had pink nail polish (the colour of the craft foam below). It is definetly a fine line to walk between light weight and durable.
To those who have requested the files, now that things have calmed down I will post them, but keep in mind the scale, they are scaled for someone who is 4 feet, and you will need to cut some of the openings larger, like the head and arms.
Now that I have done this one, I may consider doing another one with more detail over the winter and do all the little bits that need to be done. I want to use it for next April, but there is a good chance he is going to grow a fair bit over the next year. So what to do, what to do.