One of the biggest issues when shipping a sculpture is survival. Will it make it to its destination intact? The best packing in the world can't always guarantee safe travels. There are too many variables between point A and point B. Check YouTube for some "worse case scenarios".
I like to make my own boxes and internal support structures. I also like to include some detailed pictures of the sculpture in relation to the box. I want the recipient to know the best way to remove their newly purchased piece.
How to ship SecondHand Superhero? This one worried me. I did have a fairly substantial framework hidden inside her "jet stream", but this is the kind of piece that had to be supported. This gal needs a seat!
A piece of Masonite was cut to the inside dimension of the box. I then securely attached some thick cardboard tubing and a "seat". The seat was then covered in a soft material so as not to damage the paintwork.

Once SecondHand Superhero was snug in her shipping box it was time for the big dump. StyroFoam popcorn! The box lid is taped on - shipping label attached and fingers crossed.
...and she made it to her destination safe and sound.