There are no instructions for additional shipping charges for physical add-ons, so that must mean they are included with the $18 shipping for the physical tier.
I think the only extra fee you may have is customs ($5 + GST on the value of the items, which is less that the tier pledge). DVD sized packages can often get through without an extra charge, even when above the $20 (IIRC) limit, but I'm not sure about a poster.
