[xmonad] Set Window Maximum Width

Hi, I use a fairly large monitor (24" widescreen). Most applications I open, are too large when they take up the entire space, and I end up needing to open another application (like a terminal) to shrink them down. I was wondering if there's a way to set a maximum window width. So if only one application is running, it would float in the middle of the workspace? It would be a plus if this size can be set per application type (e.g. window class). Thank you,