Hi everyone. I have a wedding topsy turvey cake in a couple of weeks and in 2 dry runs the past few weeks, both times, my bottom tier wants to just fall apart once I finish stacking. I have plenty of support and I wouldn't think it would be a problem, but I just cannot figure this out! PLEASE HELP ME!!

"my bottom tier wants to just fall apart once I finish stacking"

I'm thinking your bottom support isn't really "supporting" or it could even be over-doweled. Having too many dowels can cause the tier to split apart. Do you have an after photo? What support to you use? Wooden dowels, bubble tea straws, etc.... How many in what size tier? How far apart?

May be your cake is extra moist, moist cakes are delicious but always cause problems in stacking, choose a cake with firmer texture specially when you are making cake with more than two tiers.
Let us know how things ended wish you luck

I used the smooth-edge cake separator plates with the hollow pillars (used dowels before and it did the same thing on my first attempt). I am also using a WASC doctored cake mix recipe. It's a pretty dense cake. I wondered if I'm cutting into my cake too much for the next tier to sit on perhaps and not getting enough of a tapered angle toward the bottom of my subsequent tiers?