It would be fair enough to say that a CAT score cannot be directly compared with the 11+ because they are standardised differently, but SATs predictions are perhaps even less reliable! Personally I never came across an appeal panel that wasn't interested in seeing CAT results.
If you want to study the relationship between CATs and the curriculum, you will find more information here
http://18.104.22.168/search?q=cache:L5 ... clnk&gl=uk
but most panel members probably won't be familiar with CATs as a predictor of success in curriculum tests. They will just look at them as alternative evidence of ability, and I think that is how you should present them (not as an alternative to SATs). The scores should be more than above average - to make a good impression they should ideally be 'well above average' and towards the top end of stanine 8.
The point of an appeal is that you can introduce alternative evidence. Most appellants are going to have SATs levels because most children attend state schools. In your situation - without SATs - you need to ensure that you have as much alternative evidence as possible. See here for the different types of evidence:
http://www.elevenplusexams.co.uk/11plus ... rs.php#b11