Need shipping advice

[colorjunkie]

Greetings! I have been blessed to have a couple of my recent landscape images become quite popular, with many requests for prints from all over the world.
Wow that feels great!
I am offering three formats for each image; inexpensive poster prints, medium priced large format prints on metallic paper shipped flat, and high end aluminum fine art versions which would again be shipped flat after I sign and number them.
I need some advice regarding shipping prints out domestically and internationally.
Domestically, I’m planning on shipping the posters rolled in tubes and having my print lab drop ship large format metallic flat directly to the customer. The aluminum would come to my studio, be signed and numbered with a COA, and then be repackaged and sent on to the customer.
So there’s two shipping charges involved in those.
But internationally, I’m coming up blank. I can ship rolled tubes internationally but can I ship flat that way too? How about the big aluminum (60 inch) prints? What’s the best company to use for this? What have you done? What problems have you encountered? I have this vision of a nightmare of broken packaging and bent corners on the aluminum causing returns insurance claims and dissatisfied customers.
I’m going down to the UPS and Fed Ex stores next week to consult but I was wondering if anyone reading this had already been through this? Perhaps you could save me a world of headaches from your own experience, I would be most grateful.
Thanks in advance!