Every time I have tried to make a 8,7,6 and 6,5,4 round cakes for the mad hatter cakes my top slides and the seconds tier doesn't hold up. Am I not using enough supports, I use the same supports you would use on a regular tiered cake. Thanks to anyone who can help.
What kind of cake are you using? If it's collapsing every time it's probably just too soft. The sliding would mean that you're using a filling that's too soft or too much of it.
Try it with a firmer cake and just a LITTLE buttercream in between the layers. Since those sizes are both pretty small, you'll need a firmer structure to hold up the crooked shape of them. If the bigger tiers slide a little it's not so noticeable, but if the small ones go it's going to be way off by comparison.