1) PolarBear cooler (24 can size).
2) Vac pack(after seasoning meat).
3)Fully fill cooler (Freezing bag 24hours or more is beneficial too). Have "extra" small amounts of sausage or other "extra" frozen stuff to pack every bit of bag.
4) Do Not open "to check" enroute
5) After 12 hours door to boat, still frozen even without prefreezing cooler.
6) If more than 12 hours , insert small amount of dry ice (5 pounds allowed per bag...maybe per passenger). I have travelled with 2 bags, but only 1 per passenger and no problems. Using Dry Ice of 3 pounds, we went 24 hours door to boat and arrived frozen solid.