Hi all - first post question here!!

Were making a cake for my sons christening tomorrow, just a simple victoria sponge, the biggest recipe we can find however is for a 9'' tin and ours is a 12'' Square.

My mum has tried to work it out and thinks its a 14oz recipe so

14oz caster Sugar
14oz Flour
14oz Marge
7 eggs

is this correct or will we need more? The tine is a deep one, about 4 inches deep.

Thanks in advance - and everyones cakes looks really beautiful, I must say you have all inspired me a great deal!