The next time you make it would you do it the same way regarding the sponge or would you only make half the batter?
I would make the same amount of sponge cake batter and only use half or a little less than half for the cheese cake and use the rest in a mini springform pan and hope half the amount would rise and bake well for the cheese cake. I had never made a sponge cake before and did not know it would expand like it did. The batter looked just the right thickness when poured into the cheese cake pan. Maybe a thinner layer would not bake as well?