If she is not flying,my wife takes her Nikon 600.She went on a trip to Anartica and rented a 400 which was very good. In Manitoba,she used her 80-300 I belive it is, as the polar bears were all withing 50 yards.
At the time of purchase,there were only 3 each 600mm lens for sale the US. She was lucky enough tha tone of the personswho was going to buy it in Japn canceled out
I was the the primary gear packer, and a 400 is just about all one wants to lug very far. The big 5-600 also take a lot more stable tripod