Flew with my little fox-terrier for years in Africa, mainly in C210's and C404's. He loved it, would eventually jump into any open aircraft in the hope of a flight. No problems ever, except maybe that he was always trying to eat the refueller at Jan Smuts. He even went up in gliders with me, turbulence didn't bother him a bit. Go for it, he's a dog, he'll love it!