I am stacking 3 or 4 9 inch cakes (each 1 1/2 high) and then need to place a bowl shaped cake on top (7inch at base) do i need a cake boerd and dowles in between the stacked cake and the bowl shaped cake? I hope this makes sense! 
I can hear people cursing me now but i need to assemble my cake now. So....BUMP! 
If you're going to transport it I would put a dowel through the center of all the stacked layers. Since they are all the same size I don't think you need to use boards or dowels between them. If the bowl shaped cakes is smaller you might want to put it on a cake board and dowel below it. HTH
I put a cake board between the bowl cake and the stacked round cakes in my Fall Basket cake. (and used dowels) First, I was worried about it shifting/sinking. Second, it allowed me to be able to cut reasonably-sized and shaped servings, rather than really tall, thin pieces.
If you will be transporting it, I also recommend using a long sharpened dowel through the whole cake.
HTH.
RedPanda
OMG!! Thank you guys sooooooo much! CCer are my life savers as usual!! 
Firstly without boards between how on earth are the recipients going to cut the cake/ secondly I would definetly put boards between each and dowel. It is not worth the aggro Good luck as you can see we all have different opinions. My cakes are very moist and soft and therefore a support system is vital are your cakes dry and able to support 4 other cakes. Cardboard between will create ease of cutting, plus if you are taking the cake you can assemble on the spot. Goodluck let us know the outcome.... I never take any risks with my cakes totoooooooooo much work involved infact I like to transport them myself and offer my stand...which is always accepted.
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