So I was watching a couple of episodes of Cake Boss. My question is, how do they put what appears to be a 1/2" of filling between their layers, and not have it bulge out? I see the decorators use a huge star tip to make the dam, and then they throw in spoonfuls of filling/icing and level it out. I know they probably leave their cakes to settle after filling, but even so, when they put the fondant (fondont ) on they get no bulging? How come?!
They also put a thick layer of buttercream under their fondant. My cakes don't look like that if I put that much on!

I hear you on the amount of filling. When I've tried that much filling (even with a really thick and sturdy filling) it continues to bulge for days!

Perhaps Buddy Valastro is a lurker on here and he might pop in and tell us some secrets

I try to look closely at the techniques used by the bakery. They can throw around large sheets of cake with just their hands and they don't break. The filling looks unusually thick and stiff too. I am sure his cakes taste good, but I bet the cakes and filling are very dense.