Actually Worbla has a lot of more uses than only creating surfaces like armor plating and such! When heated it can be shaped into any form, it kinda feels like a mixture of clay and hot glue. I actually sometimes use it as a subsitute for the latter whenever I don't want to create the typical hot glue mess and / or I want to get more control over the result. THis works since it sticks just as fine to surfaces, but it doesn't get completely fluid like hot glue does!
Here is an example from aoversized pocket watch build for a White Rabbit costume:

Notice the Worbla at the corners of the clockwork, those four spots were enough to hold it tight and secure!
I never throw away any Worbla, even if it is the tiniest leftover but collect it in a special "hot glue replacement" bin

(At least in Germany the price of hot glue compared to Worbla isn't really that big a difference compared to the weight, so it doesnt't really hurt.)
BTW, if you really want to see what one can create from Worbla you should check this facebook site:
https://www.facebook.com/AccessoriesForTheUniverse
Those guys create amazingly detailed stuff (mostly He-Man related accessories for the action figures), most amazing piece is this one:
https://www.facebook.com/photo.php?...914.-2207520000.1384499140.&type=3&permPage=1
https://www.facebook.com/photo.php?...914.-2207520000.1384499140.&type=3&permPage=1
As for stiffening the inside of armor parts:
The above mentioned Kobracast is a very nice material too! I used it to strengthen the inside of both foam and paper pepakura helmets and it came out nicely, using to layers of Kobracast creates a very stiff surface, due to the cloth in it. It is even possible to cover it with resin to get even more strength, but not as much as you would get using the standard fibreglass / epoxy route...
Main let down of Kobracast is it's texture though, due to the cloth it will look like, well, cloth, unless you cover it with any sort of filler. It is not sandable due to the textiles inside, even after soaking it with resin it was a mess...
Nonetheless: Both Worbla and Kobracast are great materials!
