I recently had two custom shipping boxes made to ship some vintage ('84) Heresy speakers from ID to NC. Freight company did a great job and speakers arrived in perfect condition.
Dimensions: Exterior "20x24x28 inches, Interior (foam cavity) 14Hx16Wx22L, Weight 9# per box.
I will offer them free to whomever can arrange for the shipping. They cost me $40 each so I hate to just recycle them.
Dan