use the dam method and you won’t get the bulge. After you have dam and filled and stacked you then shave the exterior of the cake with a knife to ensure the sides are straight. After that fill the centre from the outside pushing the buttercream into the joint.. Crumb coat and refridgerate. Pull out and buttercream and put back in the fridge for a few hours. Then fondant nice and thin. Then refridgerate again. All of my fondant cakes are in the fridge, with flowers, figurines everything. Never ever had a problem. I use IMBC so my cakes have to be put in the fridge.