Friend that flew for Vintage Props & Jets said they'd always have 'stuff' for the customs officers in Marsh & Treasure. Turkeys around thanksgiving, video gaming systems around christmas, tires in April... they were never "bribes" per se... *knock on wood*
And it obviously worked, I recall getting a ride with them to Treasure Cay, one of the immigration ladies was sitting at the podium eating her lunch with some (obviously) passengers and crew waiting on the side. When we pulled up, she dropped her sandwich to clear us and it was off to the beach. I'm not sure the other pilot and his people were too happy.
I later spoke with some friends at a charter outfit who said that if they were a MINUTE past 5PM, they'd get nailed with massive overtime fees - and apparently this never happened to the Vintage flights...
so yes, get to know the customs folks.