I'm having a hard time trying to figure out the chances of a double deviant because this bit from the FAQ isn't very clear: The chances of getting a deviation on each color parameter still remains 1/10 so the babies with double deviation are extremely rare and valuable.

Also, how would breeding 2 double deviants affect the odds?

As far as I understand it, the odds would be 1/100 (1%), since you have 10% chance for the colour deviation and 10% for the pattern deviation. Both have to occur separately to give you Double Deviant.

I don't think that breeding double deviants would change anything since deviation itself isn't inheritable. Not having tried this myself though, I can't be sure on this. 

I have a double deviant..............not even sure how THAT got pulled off XD