What do I have here- breed?

We recently adopted this guy as a 5 year old Rhodesian and we're at least the 3rd owner as far as I can tell. Do I have a Black Mouth Cur? He's nearly identical to our neighbor's BMC they use for hunting. Over the past few weeks I have some doubts as to his Rhodesian background. He doesn't have a ridge on his back. He weighs about 63 pounds. He has a pink tongue/inside cheek but a black roof inside his mouth. He has webbed toes, which is out of place for a Rhodesian. He hates getting a bath, but loves swimming at the dog park with the labs. We've taken him to a teaching hospital for his shots and wellness check (UC Davis vet hospital here in California) and they weren't too sure themselves about his breed.