Noob Validation Custom Rule Function Quandry

Thanks for the suggestion, I originally had it like this, but found that I could move the setting of the rule group into the call to validate, using: $validationResult = $this->validate('user_signin');

I have taken it back to the way you suggest, just to be sure that I hadn't hashed something up the first time, but it still doesn't seem to be what triggers the additional data to be passed to the custom rule's method.