I would love some advice on making a 4-5tier dummy buttercream wedding cake.

I am making a dummy cake for an event- it will be covered in buttercream and have an old fashioned wedding cake look with buttercream piping, separators and columns. I will decorate the styrofoam dummy in advance and then assemble on site.  Will the separator plates just sit on the top of each tier? Should I attach them in some way? Because it will be rather tall and the styrofoam is light, I'm worried about it falling over. Also, If I want to do a double height tier should I glue or tape two dummy cakes together?

I'm thinking of doing an  18" round base, topped with the tall Roman columns then a 12" tier, short columns, 10" tier, tall columns and a 6" tier at the top. I may make the 12" and 6" tiers double height. Please help!

Styro is very stable:)  No need to attach the plates unless you really want to.  If so, just put a dab of fresh b'cream under the plate.  No need to glue or tape the dummies together.  Again just a dab of b'cream w/hold them together.  If you look through my pix on here, some of them were dummy cakes for display in my shop over the years.  

There were all made as display cakes for me shop.              http://www.cakecentral.com/gallery/i/1383943/different-shapes       http://www.cakecentral.com/gallery/i/1332904/peach-and-blue-wedding        http://www.cakecentral.com/gallery/i/1330216/hearts-aflutter     

http://www.cakecentral.com/gallery/i/1330216/hearts-aflutter           

Thank you so much. I ordered everything today and have kind of figured out an assembly plan. I will have a little bit of time to play around with it so I feel comfortable. Luckily I found taller styro dummies so I wont have to even worry about gluing them together.