Tearing my hair out, please help me!! I need to make several Christmas cakes, all different sizes, and every recipe I look at gives different quantities! I'd like to use Delia's recipe, but the cake sizing chart doesn't go up to 12" square, which is one of the sizes I'm making. How do I scale up?? And - how can I make it easier for myself - what's the secret to the maths of scaling up recipes?? Thank you!!