I want to create something similar to this for my son's 5th bday in 2 weeks.  I dont have much experience with square layers.

Any idea what size these tiers are?

I'm guessing the bottom tier is a 12x12 (but it looks higher than two layers to me?)...or maybe 10x10.  Can anyone tell for certain?

I'm considering making 12x12 and three layers for the bottom, a false  9.8in middle tier, and 6in real top tier.  Assuming supports are done correctly, will 3 layers in the bottom tier be a bad idea in terms of how sturdy the cake is?  Can i get that height with two layers in the bottom tier?

I'll make the bottom WASC. So assuming this is a 12x12, would a double recipe of WASC cake be enough to get the bottom tier nice and tall like this?

If you want to make sure you like the dimensions that you've chosen, you can use a piece of graph paper to sketch your cake. Use one square per inch for each tier and you will be able to visibly see the proportions that you've chosen.

This looks like 6", 8" and 10" to me.  Idk, I dislike using dummy cakes if I can help it only because I have the dandiest time (rolling my eyes) with getting the fondant to stay, let alone not tear at the top edges.  But on the flip side, dummy tiers will give you time to decorate, so that's definitely a plus.

Three layers on the bottom tier will not affect how sturdy your cake is if the cake and dummy cakes are correctly doweled and supported.  If anything, three layers on the bottom might eliminate the need for the real cake on top, simply because of how many servings you will yield.  They may have also used two layers on the bottom and put a 1" dummy piece under than, then covered the whole thing in fondant.  There are many ways you can configure a cake like this.

hth

AHow many servings of cake do you actually need?

i'm thinking the top tier is 3" smaller than the middle tier and that tier is three or four inches smaller than the square bottom tier--

so either a 6X9X12

or a

5x8x12

this chart http://www.wilton.com/wedding/wedding-cakes/wedding-cake-data.cfm  tells you how much cake batter to use--for example i get 16 cups of batter in a two box wasc recipe -- but now the box mixes are smaller and it's too confusing to say with certainty because there's too many variables so just measure your yield and write it down so you can keep track and use the chart for the right amounts-- for a 12" square it's 10 cups of batter for one layer so i would mix three boxes and have some lefpt over for a 2-layer 12" tier

The bottom tier looks like a 6in in my best attempt to judge from a picture... So my best advice would be determined on your cake pan sizes, if you have 2" pans Id suggest three layers, if you have 3" pans id suggest two layers depending on your skill for leveling cakes and how much filling you generally use... HTH

My pans are mostly Wilton, so I think 2in. deep. 

As for how much cake I need, the RSVPs are still coming in.  I would say minimum 30, maximum 50. (this accounts for parents plus kids).  I will email the non-RSVPers when it gets closer to the date, however, I need to start the cake before then since I have limited time between now and his party.

I can easily add cupcakes at the last minute for extra servings if I need to.

I re-checked my pan sizes and don't have a 12.  Also, my false tier is just under 8in, not 9.

So, I guess I'll do 3 layer 6in top, false 8in middle, 3 layer 10in bottom. 

That should get me to 50 servings, correct. 

Alternatively, if I do a 3 layer 6in top, false 8in middle, 2 layer 10in bottom (sitting on a 1in false 10in layer for height), where would I stand with servings.

It has been a year since I stacked a 3 layer cake.  Do I center dowel it if I have a false tier in the center?

Thanks!