I'm making a 4-tiered wedding cake this weekend where the top 3 are real cake and the bottom one is a dummy. Should I put the center dowel through all 4 tiers down to the cake board, or will the dummy potentially split if I try to push the dowel all the way through? Thanks...

A styrofoam dummy won't split when you dowel it. Trust me, I've reused dummies over and over again, and there are dowel holes all over mine and never a split!