Issues with Global Shipping Program for combined shipments

[curiouserandcuriouser]

I'm having a serious problem with the way eBay handles Global Shipping for combined purchases in one shipment.

Had a buyer in Germany purchase 4 posters at auction, which I combined into one shipping tube. eBay would not allow me to send a revised invoice for a combined shipment. The only way to process the transaction was to have the buyer pay shipping 4 times (one for each poster) to the US Global Shipping Center, and I then had to go back to PayPal and refund them the difference. I then had to call eBay to ask them to credit fees associated with the additional shipping charges.

Further, the buyer advised that they were being charged customs on each listing, rather than as a single shipment. Here is his description:

"I have to pay customs of 19 % also on the shipping costs and when I pay 4 times shipping I have 4 times to pay customs and when you send back on the difference with paypal I lost 3 times of customs."

"I often buy posters in the US and never have these problems ... If I bought something, the seller from the United States shipped the goods and gives the value exactly (outside on the package) ... then the package automatically goes to German customs and I get a notification. Then I have to submit a customs application and pay import tax (no customs, because art is duty-free in Germany). if i original Chagall or Picasso posters bought so I have to pay only 7% single tax (reduced rate on original art) ..... if I had received these 4 posters as a normal program (without this stupid "ebay program") then I would have for the entire shipment only have to pay 1 time shipping and only 7% tax !!! that means I have lost a lot of money by choosing this program .... Other Ebayers in USA can sell without the program.
o.k .... I have made the payment and will not buy anything next time what is set with this "International Program"

I find this to be a flaw in the Global Shipping program, and it's making me consider opting out of it altogether. Is there no other way to handle this issue? Can the policy be altered to make combined shipping possible?