Lipo sacks are for pansy's... Theirs nothing to be worried about when charging a lipo unless your a complete idiotic moron who cant read a manual on how to charge a lipo, then you've got some issues... But seriously, lipo sacks serve no purpose if you know what your doing. Plus Ive heard of cases were lipo sacks have failed on larger packs.
I have $80 of lipo sacks, $1200 of Neuenergey 30c lipos an some really shady ones ive bought off ebay. I have never had a lipo puff, spark or fart while charing with the 061iduo, If you have a bag of sand or charge them in in an ammo can or or home made bomb lipo shelter, I agree you shouldn't be messing with these in the 1st place LOL