Window Size

Is there a way to set a different window size beside the preset one, I'm playing on a dell u2711 with a 2560x1440, but I like playing with only about 75% of my screen occupied while I can use the 25% for yg, etc. So far I can't find any res that can do that, 1920x 1080 or 1200 window size is to small on my monitor. I remember back in FFxi you could go in regedit and set your own res, wondering if you can do the same with 14.

If you open the FFXIV Config there is plenty of resolution settings available.
I'm looking at mine right now, and I see over 25 different screen resolutions I can choose from, from 1024x728 upto 2560x2048.