This is how I package big planes for sending USPS.
I've been through a couple of mishaps, broken planes I have received.
So when I ship one, I build a wood box.
I disasemble the plane, anchor the plane base in the box with two notched blocks that sit over the sole, front and rear.
Then I bubble wrap everything else, install the top with screws.
Then I wrap with heavy paper, address, and send.
This just takes about 30 minutes time to do this, and really helps when the plane is dropping off a 5 or 6' elevator system in the post office.