WXGA 1280 x 800 is the lowest standard 16:10 resolution.
640 x 480 & 800 x 600 are both 4:3, so you will get the black lines down the sides or it will pull out of shape & squares will become rectangles, faces will become fatter.
If you want a low resolution, then 800 x 500 & 768 x 480 are 16:10
If you can divide the X axis by 16 & multiply that number by 10 & get the Y axis, then it is a 16:10 and everything will stay in proportion.
I have a 16:9 monitor & play at 1280 x 720, I played without a GUI mod & the writing was small, but certainly not unreadable. I have since installed the GUI mod & have the fonts 40% bigger. To me now they look a bit too big & before my next playthrough I will drop it to 20%.
[URL=
http://img23.imageshack.us/img23/1075/1280x720w.th.jpg[/IMG][/URL]http://imageshack.us/photo/my-images/23/1280x720w.jpg/][IMG]http://img23.imageshack.us/img23/1075/1280x720w.th.jpg[/IMG][/URL]
This image is 1280 x 720 with +40% fonts.
Edit: That didn't work well, Imageshack shrunk the image to 800 x 450