Copy monitor just doesn't work when it comes to the size of columns changing. I am having the same issues on my project and after looking at a lot of other web pages I have found that this in an Autodesk issues because it isn't a feature of the copy monitor tool. It will only allow you copy and monitor the X,Y directions and if it was deleted. I did see that it was in the wishlist for future releases of Revit. So cross your finger and maybe it will be feature that is added in 2016...