Hello!!

It's been a while since I've done a topsy turvy and I can't remember what I've done in the past.  I usually fill my cakes using a dam and let them settle for at least a couple of hours, then trim, crumb coat, yada yada from there.  

The problem with a topsy turvy is I need to carve the sides down so they are tapered.  If I fill with a dam, let them settle and then trim I'm cutting the dam off of at least some of the layers and exposing the possibility of filling bulges.   If I trim it and then fill and let it settle, I'll probably need to trim the sides again, yes? 

For the record, I'm only filling with vanilla american (50 butter/50 shortening) buttercream, but I usually dam anyway.  Once they are settle I cut the top on an angle and make them "topsy," so that part I don't have to worry about.

Can you tell I'm over thinking this?  What do you usually do if you usually let your cakes settle?

You're overthinking this. If you're only using icing as a filling you don't need a dam at all. Assemble the tier, give it a good press to squash out any air bubbles, let it settle if you want to, then carve it down. You'll be fine.

I don't make them often, either, so I refresh my memory with this:

http://www.cakecentral.com/tutorial/20224/how-to-make-a-topsy-turvy-whimsical-cake