I just ganached a 5" cake that is 6" high (two 3" cakes, torted and stacked, filled with CC icing and ganached with dark ganache). So far, the cake feels super firm and sturdy, but this cake is a shower cake for a bride that has also ordered her huge wedding cake from me. It would be absolute disaster if this tier was crushed. I plan to stack this tier on top of a 7" round, and top the double barreled tier with a 3" round. I have planned to use my regular internal supports, but after seeing the height of the finished double barrel tier, I am nervous. Is this too tall to hold itself up? Should I slice into the tier and separate the top two layers and board and dowel them?

Sorry this post is rambling. I hate to do extra work, but dont mind at all if the extra work will save me from disaster! :)