sorry steve, that i didn't post this sooner for the lynxes...

i ran across a tiktok video a while ago and utilized that info for mailing a kite. i was able to use a MUCH smaller box for the kite and bag, and saved a few bucks in shipping. with mailing costs going nuts lately, this could potentially help you.
https://www.instructables.com/DIY-Vacuum-Packing-aka-the-Poo...
i used a regular garbage bag and a shop vac to suck a kite and bag down to nothing-ness. it is truly amazing how much smaller these things get.
i take the kite out of the backpack and fold it over as much as needed, fold the backpack in half, stick them in the bag, and give it the ol' suckeroo. i used a wire bread bag tie to seal it and that worked well, saving me the trouble of tying a knot in the bag and potentially having to use a larger bag to have the extra material needed for the knot.

Great tips Tom! A lot of times the size box a kite comes in is based on what old boxes I have on hand from recent purchases. This method no doubt would greatly reduce the bulk. Don't forget to add that extra layer of cardboard to the top and bottom to keep folks from cutting the kite when they cut free the tape.

I'd further suggest wearing safety glasses when opening one of these vacuumed specials, particularly if you just bought a used DP kite. I'd hate to take one of those pulleys in the eye when everything bursts to full size! :P