How to pack a model for shipment and not be worried.

So I need to pack this P-51D for shipment to Va. in a few days and I don't want it to take any damage. I had a Priority mailbox that was the correct size for the model and the mirrored base and was eight inches tall. So I went to the fabric store and bought some solid foam core that would normally be used for making pillows and was four inches thick. I had the girl slice me off a section that was a foot wide and two feet long .... $6.75. Once home with my purchase I cut one half off to the size of the box, I placed the model on the foam and traced around the propeller, landing gear area, tail wheel and pitot tube with a marker. This gets cut out with an Xacto knife. So far about ten minutes have passed. I test fit the model into this hole - everything looks good. Now I cut the second half of the foam core to the same dimension as the first and lay it overtop the first section (model is on the workbench right now, not in the foam). Carefully I lift one corner until I can see the lower hole and place a mark at each corner. Remove the top piece, connect the four dots using a ruler and cut the top hole, note the hole only covers the central area of the model. Test fit the model upside down into the top section - fit is good, total elapsed time is 20 minutes. Now I pack the mirrored base into the bottom of the box and place the first section of foam in place, the model goes in and the second piece goes on top sandwiching the wing tips and the elevators in place. A few quick packing instructions are printed on the foam and we are ready to go. Once the box is sealed the model CANNOT MOVE. Total elapsed time about 25 minutes, total cost of packaging $6.75.