If you feel it necessary to double-box using a certain carrier, then that carrier (shipper) shouldn't be used. 

 

I've recently transferred (shipped) and posted many items without double-boxing--even delicate items such as cameras, with no delivery damage. 

 

For packing material, I like to use bubble-wrap; it does a fine job--quick and easy. Recyclable, it can be reused many times until too many bubbles are popped. Probably for the best reason, it doesn't leave the recipient an unpleasant mess as do the foam "peanuts".

 

I used to run a freight-transfer / household-moving company; I never saw a need for double-boxing. If the item is packed properly, and the proper thickness carton used, damage will be avoided.

 

Remember, the carton's thickness should be relative to the size and weight of its contents. Generally, the larger the carton, the thicker the walls of the carton should be unless the item is relatively light and unbreakable. The same applies to smaller packaging of heavy items; the heavier the item, the heavier / thicker, the box should be.

 

Richard Stuart Otto, 14 April 2007