I am making a 4-tier squre wedding cake next week (18-14-10-6 tiers). The bride wants the bottom layer to be Rice Krispies and the top styrofoam, but the middle two layers are real cake. Do I need to put support dowels in the Rice Krispie layer because the cake is heavy or are the Rice Krispies strong enough to support it? Thanks for your help!

14 & 10 are still pretty big layers, I think I would dowel just to be safe. My RKT are always a little 'smooshy' ...

I would definately think so , specially if these cakes will b filled , thats going to make them alot heavier. But Im not a proffesiona, you might want /need other peoples input maybe with a little more experience.
Good Luck !!!