That sounds like the correct size. The safest for a dog is one they can enter and just turn around in. They do not need to stand fully as the dog will mostly be laying down. A travel kennel is basically the dog's seatbelt and too large of a crate may not protect the dog to the best of its abilities. You don't want the dog traveling very far before contacting the side of the kennel in the event of a sudden stop or a crash. Air travel requires a larger crate but that is not applicable here.
