I sell internationally but my postage costs is always $2.75 ($1.95 for asian countries).

I would block Germany and Canada, because postage is extremely slow.

Also block Russia, Israel and Brazil, they seem to never get orders when you send it to them.

Also your DSR ratings are going to take a hit, because postage world wide is very inconsistant. Some are fast and some are slow and it changes.

World-wide posting system really sucks.

My items all fit inside standard letter standards, so I don't bother with customs forms (I buy international stamps and dump it in the mail box so I save HOURS). It always been fine for me.

Tracking is ridiciously expensive, even at the cheapst in australia post it costs $60.