I have shipped several with regular old FedEx. You can try taking backs off and cushions off and mix and nest in suitable boxes. Two boxes or more. Stores that import from China and elsewhere have heavy duty boxes in their dumpsters. As always, the trick to shipping is tight and no sharp corners unprotected.
I am talking stock, bucket bomber, folding panel seats here.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn