Jetpack – Twitter Cards – Override card type for certain pages…

From other questions/answers I understand Jetpack dynamically chooses the card type.

I want to override the card type (and some other twitter parameters) for certain pages.

I use PHPAnywhere and CustomFunctions to add PHP to my sites without updating other code that many be overwritten during theme changes/upgrades etc.

What code do I need to detect the page type and only in certain instances change the Jetpack Twitter settings?

The pages needing changes already have a custom rewrite rule – in my custom fuctions – so if the code could go in with that so much the better!