I've only done 1 pillar construction and it seemed easier than the stacked construction. I've done several stacked and still have a bit of trouble putting the smaller layers onto the dowels.
You would want to cover your cakes with the fondant first then an easier way to stack the cakes on the dowels would be leave about 1/2 of each dowel sticking out of the cake then place the smaller cake on the dowels. What will happen is the weight of the smaller cake will push the dowels down into place.
Well, I have only iced them with buttercream. (my stacked one was with fondant and was "finished" before stacking) I put a crumb layer on, stack them securely then after they've dried real good, finish icing.
I will definitely try the half way in trick with the dowels next time though!!! I can't get over how I seem to learn something on this site every time I have a problem. Thank you 
My fingers always get in the way 
Thanks!!!
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