"How would I prove this out. By breeding it to a true axanthic would not help would it? Any ideas?"

Breed it to a normal that way you're not mixing genes. It will make it easier to follow the genetic markers and outcomes. It is possible that some genes can affix themselves further compounding your outcomes before you have them figured out. I believe Kevin McCurley had this issue many years ago. Dig around and you can find his comments on it.

Or,

Simply send it to someone that knows what they are doing.