Rafer Ties
The old ceiling was constructed so that the ceiling joists didn't run the entire length of the house uninterrupted. Two pieces of wood were nailed together and would lay on top of the walls, even though none of the walls were technically load-bearing walls. So when I took a couple of the walls out the ceiling had a tendency to flex quite a bit.
So my Dad and I nailed a few steel connecters to the joists and now it's totally solid. The ceiling doesn't move up or down now. In other words, steel rafter ties are the Mr. T that holds the whole crime-fighting, gymnastics team together.
Also, here is a picture of the inside of my skylight that shows how sloppy looking things are behind the scenes. There are a lot of pieces of scrap wood or flooring that aren't really attached to anything except the wood lathe. Sometimes it seems like the houses were build out of whatever was laying around. The riddle here is how to insulate around it.