I know i used this for my chest plate on my ncr costume, but i think it would actually be a very viable method for making durable, well fitting breathable undersuits for the hale armors out in the forum.

what you will need:
-Contact Cement, the brush on both sides let it dry kind.
-Foam floor mats, most everyone here seems to know this now
-an under armor (or knock off) shirt. any shirt would most likely work but i wanted the tight fight of the underarmor
-a brush or two, dependent on what size of cement you it may/may not have a built in brush.
-a veeeeery well ventilated work space, and or respirator, and an old shirt you dont mind possibly messing up.
*note this shirt is to be worn under the underarmor shirt, the fumes from the flashing glue will sting your skin in direct contact because under armor is so thin, once it is dry this will no longer be an issue though. If you have a dress form all the better, but do not try gluing the foam on unstretched material or it will not fit properly when worn.

1So first draw out your patterns and cut em and pretty um up the way you want, this will be very difficult once on the shirt.

this is the shirt i had laying around, i had cut the lower half off the sleeves for a different custome. and the next pic is the glue i used, i used that entire bottle, so the next size up can may be needed.



2. Put a coat of the glue on the back side of the foam, no too thick yet, then carefully line it up, and firmly press the piece into place, then immediately, but slowly, pull it away and grab the "cobwebs" with your free hand as not to make a mess, now you will have an area of left over glue on the shirt as a template for where to spread the actual coat of glue, so put a thin coat on the shirt, and a nice coat on the foam, let them dry as directed, and then firmly push it into place and hold for a few minutes, pushing all around the edges and center, that piece should now be firmly in place, and you can move on.





once you are finished wait about 20 mins before carefully removing the shirt so you are not as likely to tear away the foam, look around and look for any edges that weren't glued properly and tend to them.
I let mine sit a day or two, then took my heat gun and shaped the foam as normal, the heat doesn't ruin the spandex/elastic as long you keep it on the foam.

I then took my hot knife and proceeded to score and mark up my chest, then gave it two coats of mod podge matte (tho i don't think finish matters) going in a 45degree angle over the entire piece to give it a brushed steel texture. next i did the same thing with some silver paint, brushed a t 45 to simulate steel.


next i brushed water based paint into all the nooks and crannies and wiped it away to give it some depth. after that i dabbled on a mixture of red and brown for rust in some spots, and boom. all finished.

and this is what i ended up with


I could see this working very well for under suits for adding that soft suit armored look as well
Thanks for checking it out.

Update**

added another piece to the chest and re painted it.
real reason for update is to talk about the durability of this. I went to a con in march and I wore this all weekend, to the dances, to a room party, and even had a friend take it off me when i passed out in our room lol (guess he thought it would get messed up.) The foam only de-laminated in a few area's, and that was only because of when my friend took it off me. So it works very well.