Title says it all. The regular creditcard:true method works fine but we don't process all the cards it checks, so I need to be able to restrict to Visa, MC, Amex and Discover - so I turned to the creditcardtypes method in the additionalMethods file and edited it to only check for those 4 cards.
But, it isn't validating anything - at least in the way I've edited it. I know I'm doing something wrong but can't see what it is. I've created a test page with the issue and have attached it here.
As always, any help would be greatly appreciated.