Steaming a larger Christmas Pudding

Hi Lindsay,
My question is regarding Delia’s Traditional Christmas Pudding recipe from ‘Delia’s Happy Christmas’ book (2009).
I always make this in a 1.2 litre pudding basin as recommended in the recipe, however this year I am using a 2litre pudding basin. I am confident about increasing the quantity of the ingredients, but my question is, do I still steam the pudding for 8 hours to cook, and 2 1/4 hours on Christmas Day, or do I need to increase the cooking times, and if so, by how much?
Many thanks, I look forward to your reply.
Kindest Regards,
Penny Miller