I have two 2-inch high 10-in rounds foam dummies that I want to use with 2 cakes same size on top. How do I secure the dummies to each other? Fill with bc or a smattering of ganache? Then I just ice them like the cake? the cakes will be on cake boards. I'm going to dowel all the way through. and just use a couple wide straws between the second & top cakes. any suggestions, tips? Thanks

I have used royal/ganache and long bamboo skewers to attatch two dummies together....place first dummy down and add a blob of royal/ganache, then place second dummy round on top and push down and wiggle...this helps spread out the royal/ganache...then take three bamboo skewers and at least an inch from the dummy edge, hammer/push each skewer in the dummy spaced evenly and then cut flush.....I do a triangle pattern.
I would then take the dowel that I am going to use for the center support and push it through the dummies. There is always a chance that if you wait to put the center dowel in after you have finished your cake...because two layers of styrofoam is so dense...in trying to hammer the dowel you may damage the cake.
Hope this helps...

Thanks. I hadn't thought of putting the center dowel in early. great advice

there is no need to dowel dummies. *They* become the support for cake.
If I understand your ? right a real cake will be placed on top of a styro 'cake'. Are each of these to 'stand alone' or are the cake/stryo sections going to be stacked on top of each other?
I always used a dollop of b'cream to anchor the styro together &/or cake onto styro.

@ kakeladi: I'm stacking the cakes on top.... making a stockpot of boiling crabs and only need 2 cakes so I thought I'd add height with the dummies.