Any rule of thumb on what the shipping could be, like for a tube of side stainless trim? Maybe the tube is 2-3 feet long? Could it be double what it would be to ship state to state?
If you're sending it through the post office (recommended), there's a 42" maximum length restriction. If you're under that, you're golden. First Class Mail can go up to 36" for a tube as long as it's under 4 lbs total. If it's not real heavy trim, but in a good solid carpet tube or similar, figure on about 4 lbs shipping weight and the cost would be $30.44 for First Class Mail and $46.40 for Priority. I do this stuff every day, you'll have to fill out a customs form but it's not bad, pretty straight forward otherwise.
I see a lot of people traveling carry somewhat long and fragile items in lengths of pvc tubing with end caps on it. a lot of fly rods get packed around the country safely that way. The carpet tube idea is a good one though. The main thing is something stiff enough that it won't get bent and you can roll each piece in a bit of bubble wrap or that foam packing sheet that comes with a lot of stuff now.
When i send parts to Oz or USA i mark the customs form as Gift, Clean Used Old Carparts, Aussie customs will go crazy if they find a dead bug or spider in the stainless trim.
Cover yourself and over quote the shipping because you can always send the person a refund for the difference through paypal. I normally don't expect a refund on shipping but it has happened to me 4 times. people bitch about being over charged for shipping but they person deserves something for handling the part,i mean the part doesn't send itself!