and then use a hair dryer and scissors to mold it around your battery. They you can wrap the whole battery in lexan, and protect it from a lot of stuff.
This is what I will do with the sheet kydex (said delrin, meant kydex!). I will make a 4 sided box, and use the left side chassis rail as the 5th side (6th side is the open top). That will maximize the battery area, as it is a bit narrow, but still leep the pack safe.