Okay, so I've watched all the videos, read all the articles, perused the galleries, but I really want to make sure I've got this down before Friday-the day I stack my first topsy-turvy.I plan on using dowels in each tier (like I do when I stack regular tiered cakes) with one central dowel through the whole thing to ensure it's safe arrival 1 1/2 hours from here (1 hour of which the client is driving-not me).

I know some of you will say, "USE SPS", but that's not an option for me right now.

I also plan on doing the "shelf" technique, where you cut into the bottom tiers to allow the tier above it to sit level. It's going to be a 3 tier cake.

-Is 4 dowels in each tier enough to support everything? (then of course the 1 main dowel through the whole thing) Is there a specific size for these dowels?
-is there a certain size dowel i should use for the central dowel? I bought 5/8" today and 3/16", but the 3/16" looks too big.
-is a cardboard cake board sufficient for the middle and top tiers?
-any other pointers?

TIA

I did one EXACTLY how you are planning yours.

I had 3 tiers, 8-9-10, 6-7-8, 4-5-6. The smaller tiers were the bottom of each cake. I used bubble tea straws in mine and a center wooden dowel.
I also put 5 straws (instead of 4) in the 2 bottom tiers of cake - the 5th one was off center so I could still drive the center dowel down through without worrying about hitting one of the other ones.

for the boards, I used 1/2" foamcore for the base cake, and 1/4" foamcore for the other 2 tiers.

Make sure you carve the hole out big enough - I had to redo one of mine - which was very stressful at the time. It turned out fine though.

I followed BKeith's method on here, but I used all buttercream instead of fondant.

http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1357281

Here are a few forums I've been watching..... I made one topsy, with minor mishap.... but you learn for the next one!! Hope you find some of this information helpful!!

http://cakecentral.com/cake-decorating-ftopic-617369-0-days0-orderasc-.html

http://cakecentral.com/cake-decorating-ftopic-613563-0-days0-orderasc-.html

The second one is full of helpful info!!
~ Jaime

those are all very helpful links and tips. Thanks, Ladies!