What is the best way to adhere a dummie top cake to a real cake on the bottom tier? Melted chocolate has worked best for me but pulls up the frosting when tiers are separated. Do you ever use a dowel through a dummie tier?

This lady i take demos with at ices convention. Always uses r/i. Even all real tiers. she dowels each tier(real cake) and then attaches with r/i. she laughs at us for using dowels. She's a great decorator.

A cake dummy should not be sitting directly on top of a real cake layer. You need to have a cardboard attached to the dummy (food safe and any dowels won't penetrate) then you can use your usual method of attaching tiers together - which is royal icing for fondant tiers or buttercream for buttercream tiers for me.