I took the Wilton Tier class because when every I started to stack my cakes I always had a problem with the icing coming off when I took the top tier off.  The instructor told us to put some confectionary flower before putting the next layer on.  Sure enough that solved the problem.    I put three straws where the doll will sit.  I also put down some plastic wrap under the doll so that no hair will get on the cake.  The oversized cupcakes are a meal in themselves.  A little layer between then just ice the top and you are ready for your party.