You will need 3 sizes of pillars, along w/cakes and plates (8 of them) all the same size.
Getting the placement right is the key and will not be easy. This is hard to put into words
Practice w/o cake on pillars & plates; (use cake pans in place of cakes) and make accurate measurements *on the table* so you will know when you set it up exactly where to place each one. Each cake above the previous one rests about 1/2 to 2/3 of the diameter on the previous one w/just two (of the usual 4) pillars in place. Continue up the line using longer/taller pillars each step of the way up. The top cake is just stacked on those two tallest ones.
*Very* careful measuring is *very!* important for this to turn out right. Each cake must be the exact height as the pillars that support it.
Oh, and doweling should be used to support the next tier. So insert a nice, fat, plastic straws BUT NOT where the two projections that normally hold a pillar are; I would put three of them, spaced between the projections which will 'dig' into the cake and help support the upper cake.
Thank you SO very much for such detailed instructions. That makes perfect sense. I was totally stumped on this one, but I'm pretty clear on how to make it work now.
A million thanks again!