Great mod! Make me think about it to do it myself to 
Thanks. The centering rings I chose help with this. They have a concave section that the bottom of the optic sits on. This allows the optic to be able to rotate some and still press on the ring evenly. So when the flat glass is pressed down all of the optics can adjust so they are all level and flat up against the glass.
The L2 takes a 20mm driver.