If your layers are between 3/4 and 1 & 1/2 inches you should be fine without additional boards. I would like a 9" square present cake to be about 4 inches high give or take.
If you are making a real tall big boxy present cake 8 inches tall then you need another board about every four inches of height. But I mean a five inch tall cake could stand ok without a board.
I agree with -K8memphis (and, believe me, she has lots of experience!). I use a board every 4 inches (every two layer, if I'm lucky!), not only for the support, but for the serving size.
Quote by @%username% on %date%
%body%