I have a friend who's wedding cake I will be making at the end of the month. She's set on a black walnut cake and a red velvet cake. I finally found a decent looking, albeit basic, black walnut cake recipe and she has requested that I use her grandmothers red velvet recipe. I will be making a 16", 12", and 9" stacked cake and covering each layer in fondant then I will do the thin fondant in layers to look like ruffles per the brides request. Well, I made a very small batch of each tonight to make sure they taste ok and while they taste fine both are very light cakes and now I'm worried how they will hold up with the fondant and being stacked. Do you have to have a more dense cake for a wedding cake? Then comes the question do I alter her grandmothers recipe to make it more dense and not tell? (like she would be able to taste the difference!) And then what do you do to make them more dense?
Sorry for all the questions, I'm just a recreational baker so I'm learning all these tricks of the trade.
Thanks

You'll be fine. Don't forget, the cake rests on the supports within, not on the cakes under it.

I've not done this, but I keep reading here on CC that if you use a cake board to press down on the cake the moment it's removed from the oven it can flatten it and compress it to make it a little more stable. But Denise is right, the straws/dowels in each layer will support the cake(s) above.

Read this:

http://www.wilton.com/cakes/tiered-cakes/
following ALL the links on that page.

Then do as those instructions say.

And while you're at it, buy any of the Wilton Celebrate yearbooks (used on ebay reasonable) for more info.

Thank you for the replies, they were helpful. I was wondering if pressing on the cake as it comes out of the oven would be enough, I'm glad it will be. Thanks again

My cakes are light and airy and I stack them 4 and 5 tiers all the time. The cake tiers NEVER sit on the cake below it, it sits on the supports in the cake tier below it so it doesn't matter how dense the cake is. I have NEVER smushed my cakes to make them more dense - no need for a dense cake if you support it correctly. If I am going to cover a softer cake in fondant, I buttercream it and chill it well before putting the fondant on to make it a lot easier. Works very well. BakingIrene is right - read everything on stacking cakes at Wilton.com and follow their directions and you will be fine.