A decade ago lots of people were making their websites to fit a 640-pixel-wide monitor, then an 800 monitor, then a 1024....
.... and now with mobile we are being squeezed down to the microformat of 300 wide.
They call that progress???
Lots of people are accomplishing this with designs that automatically resize to fit the device they are being viewed upon.
How are you handling this? If you have not redesigned your site in the past couple of years you probably have lots of people looking at your site with devices that are smaller than you expected.
And, with lots of people using enormously wide monitors... what is the upper width that you are assuming? And, is that important?
I don't know the answers to this stuff... but it sure looks like a briar patch.