just tested it - thanks for the 4:3 tip it looks great!
I couldn't get it to run in anything lower than 640x480 though
Same here! I got it to run with my desktop on 240p, but only while Mania is windowed, so the edges get cut off. If I try to run it in 240p with fullscreen, it just crashes and closes immediately. I can get it to run in 4:3 fullscreen, but only at 640x480.
Then, once the game boots just double check in the dev menu (accessed with esc key) that it's set to a 4:3 window, and ta-da! Works great.
Hope this helps solve your problem.
EDIT: Aha! I just got it to work! So for my settings, in the settings.ini file, I enabled the "devmenu=1" option under game, added "pixwidth=1" under video and switched winwidth and winheight to 320 and 240 respectively.