Hi Roger!

My own personal experience and research has been with shipping smaller packages via air freight, cars on ship deck, and at one point I researched a good bit about shipping packed barrels of goods to las islas caribeñas. But there are many others already over here on LiCR which have direct experience with shipping full and/or partial/consolidated containers from the US to Costa Rica. So hold out a bit to see what those who have done it before have to say if they chime in.
I do know that "best shipping" company and method can really vary a lot based upon the details about what you are shipping. Can you describe the cargo and what level of help you'll need to get your stuff from there to here?
Is it heavy? Are there small things? Or are all the things big? What kind of cubic volume would you estimate for all of your stuff plus packing materials (like crates? or shipping boxes?) A real rough guess would be fine.
Are you talking about the full treatment which goes something like: You buy a bunch of big things on Amazon and have them shipped to a warehouse in Florida where someone waits for all of your stuff to arrive, securely packs it on a pallet and then transports it inside of a container along with stuff from other folks? And then when it gets here, they handle passing your stuff through customs and storing your goods for you to pick up at their warehouse or they also arrange for delivery to wherever you are? Is that what you are looking for? Or some subset of that?
It's good to see you over here! A tip of the o'Chapeau to you too my friend... ;-)

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Sam