Also, get a mod that uses metal for the enclosure. Something strong enough to protect the battery from drops and such. I wouldn't trust a flexible nylon enclosure at all. It can be dropped and crush the lipo but return back to its normal shape while the battery inside suffered major damage. The enclosure appears to be fine but add an amp draw to the battery and boom, inches from your head.
I think Nylon is more flexible than alu or other tin. It can simply bounce - absorb bang in same time. (just thought).