I'm planning to install a "coffered ceiling" in my dining room similar to the project by John Casey detailed in the Nov/Dec 2013 issue of the magazine. My question relates to the sizing of the grids. Is there some rule of thumb on what looks good? I have a light fixture centered in the room, so an odd number of coffers makes the most sense to center on the fixture. If I do a 3x3 grid I end up with coffers of about 42x50. If I do a 5x5 grid the coffers end up at 23x28. Does anyone have thoughts on this? How large were the coffers in the magazine article? They don't state the room dimensions so I can't work it out.