A quick sort-of related note - I use a piezo z sensor. When it does a reading it presses onto the glass plate that is on top of the build plate. Sometimes the pressure is a bit too much and you can see deflection of the build plate and/or the printhead carriage. This is most annoying and I thought I would fix it's little wagon. The bed was spring mounted to the sub frame as a lot of printers are these days and I thought that if I removed the springs, the issue would go away. Well, imagine my surprise when I found out the build sub frame was flexing. I was not a happy camper but at this time I am not bothered enough to replace the aluminum sub frame withe a heavier plate. I am also concerned with the additional mass as the build plate is moved by the y axis.
My next printer will only move the build plate in the Z direction so I can make the whole setup stronger.