Urban Art Association

Personally, I'd ship it flat. But it does cost more of course. It might be worth talking with the courier company, some of them offer to do it all for you, costs are involved of course but they'd know best.

In general shipping in a very strong tube is most safe.
I only ship flat when it's a very thick paper, which will take weeks to flatten again.
Or when the print has thick ink or hand finished paint.
Also the value of the print is a factor. For a few hundred quid print I would roll it.
For a signed Banksy shipping flat would be best, I guess.

When using a tube, make sure it's very thick and as wide as possible.
Use craft paper which is wider then the print, so when it moves in the tube the craft paper will take the hit and keeps the print safe. Cover the front with that thin packing foil paper.

When stored flat and shipped fast it will flatten quite fast after receiving.

Basicly ; if you feel you wouldn't want to receive it rolled...... sent it flat.
In that case: use thin wood that can't be folded. Also sturdy cardboard is okay.
When you fold cardboard, it gets very strong and very difficult to bend.

Strong tube !

Use a smaller tube than the one you're using to ship it in and roll round that and then slip it out, so you don't damage it by hand.

I also tape the kraft paper inside the tube to stop it moving.

Make sure you have lots of kraft paper on both ends, and that the kraft is as long as the tube. Roll the poster smaller than the width of the tube, so that IF the tube takes a dent, it won't transfer to the poster. Tape it with a painter's tape (it's easier to get off). Essentially you don't want the poster bouncing around inside the tube. That's pretty much it.