Unfortunately I cannot find the wondermold pan in my area...and am stuck with stacking and carving 8', 6' and 4' rounds.

Will I need to add cake boards between the layers and supports?

Has anyone made a babie cake without the wondermold pan? Any suggestions on stacking and carving.

I use a 6/7/8 combo for my doll cakes.  I don't use boards as when completed the "bell" design is not that heavy of a cake.   I"m sure cutting it its a PITA though.   I tell people to cut down 2" and make a pizza wedge slice and pull it out.   Once they get the first piece out, I'm sure it's not so bad. 

I have used a small pyrex glass bowl with an upside down cupcake (flat, not domed) on top.  You would then have to carve down the side of the cupcake part a little bit to get the right shape, but it works :)

AThe Barbie will act as your supports. I've used 3 - 8" layer cakes. Stack the first two with icing in between. Then take the third cake, go in an inch and cut a strip all around the cake. Place the inside of that on top of your stack. Now roll the strip into a circle (yes it may crack but just keep it tight, it will hold). Put this on top of the already stacked cakes, this will give you 4 layers and plenty of height for a full size Barbie. Remember to put icing between all layers. Now cover the entire cake with a crumb coat. Cut a hole from the top down the center to the bottom, I use a thin serrated knife. Slide your cake over enough so you can push the cut out piece of cake out the bottom, place your doll into the hole up to her waist and start decorating. Hope this helps.

http://cakefun.blogspot.com.au/2005/08/how-to-make-barbie-doll-cake.html

Thanks so much everyone for your help!