I know that this has been discussed before, but I have a few questions.

1. In previous threads it was said that the best box is a wardrobe box from u-haul. There are two sizes and I got a large one, is this the correct one?

2. safest and most cost effective shipping. I have access to FedEx, UPS, USPS.

3. Protecting the upholstery during shipping. Bubble wrap, plastic wrap, blanket?

4. Packing material. If I wrap them up good, do I need packing material. Will insurance cover them if they get damaged and have no packing material?

Go ahead and fill me in on anything else unexpected. I just sold a pair of seats and need to ensure their safe journey from Oregon to Texas.

HIEDI

Take the sliders off the bottoms.....put them together like a spoon, cut the box down so that the TOTAL of the dimensions is less than 108 inches.

Fed Ex ground or Greyhound bus are supposed to work "best".
I think either is 45 to 55 pesos

I just bought a set of seats from MI. If you can (don't know if they are stock seats or not),
removed the sliders, and separate the seat bottom from the backrest; it takes less room that way. Mine were shipped via Greyhound, and it was pretty cheap (around $60 or so?; dunno as seller paid). I'd wrap the seats with cardboard, and then use some bubble wrap around it, as the box was very beat when it got here; looks like they stacked a bunch of stuff on it. You may want to try using some of that expanding foam insulation for cushioning the seats.
It took about 3 days to get here (much faster than I expected...).