Personally I have left batter for about 1 hour and found it changed the way it rose (not as even with more of a dome in the middle) and it didn’t rise as much. However it tasted fine. Also your rise will be affected by having the other pieces of cake inside it anyway.
The thing is everyone’s batter is different as is the environment it is kept in and so I think I am going to be really unhelpful and say it will be a trial and error thing.
Is there a reason you can’t just increase one batter and decrease the next. For example if you are using an 8 inch cake tin. Make the first batter as if you are making a 9 inch cake (adjust cooking time and temp accordingly) and the second as if you are making a 7 inch sponge? That is prob what I would do. x
CakesWorth
