So if i wanted them to be taller , how much extra should i make ?
That depends on how high you want your cake. Cakes as tender as Rose’s don’t have the strength to get too high, but you can experiment. Take whatever recipe you’re using and boost all the ingredients by some percentage, such as 20% and see what happens. I haven’t seen much higher than 1 1/4 inches for her chocolate cake recipes, but I don’t know if that’s the highest she could get or she was rounding to the nearest whole egg. If you’re OK using fractional eggs, you can scale very minutely.