The Lipo cells will always be vulnerable to punctures or impact damage unless they are encased in a hard material.
There are several manufactures that sell 2S lipo packs in plastic or carbon fiber cases. NEU energy even makes one.
I use a cheap solution from Radio Shack
http://www.radioshack.com/product/in...entPage=search
The Radio Shack project enclosures work great for many Lipo packs, you just have to put some foam in them to protect the lipo's and possible add some venting by drilling a few holes but they are only $6 or less