Stacked Cake Discussion Again

I keep reading that you should put a dowel through the middle of a three tiered cake to keep it stable.  I'm on board with that.  My only issue is that the top tier is covered in fondant and I don't want a big hole in the top where the dowel went in.  Has anyone tried making holes in the cardboard cake boards before placing the cakes on them, and then putting a long dowel in the bottom tier,  and then placing the second and third tiers OVER the dowel so  you are sure it's in the middle and it doesn't show on the top tier?  My other concern is that if I'm going down through the top, it may not be straight?  And how do I make sure I'm going to hit the hole I've put in the bottom of the cake board if I'm not placing the cake over the dowel? 

And if ya'll say "It takes practice, and you'll get the hang of it" - I gotcha, but I don't have time to practice stacking tiers before my first wedding cake is due next weekend!!  And I'd like for it to be perfect. (or as close as a rank amateur can get).  I've already had nightmares where the whole thing is all catty-wompus and falling apart.

I'm so paranoid I've already made guides out of cakeboards so the support dowels are perfectly spaced (thank you, 4th grade geometry class and "how to use a compass"), and I can mark where the center of each tier will be that I can just place on top of the cake and push a toothpick through guide holes. (does that make sense?)

Looking forward to your answers!