3:2 displays correctly on my monitor, yeah. Anyway, with some light testing that gamma adjustment seems to have fixed the issue. I did have to add --brightness=.15, otherwise it was far too dark. Thank you very much!

3:2, 720x486p, 59.94. I should add that this doesn't seem to occur with Game Boy Color games at all.

After using GBI for about 40 minutes, a noticeable flicker is on my monitor. Goes away relatively quickly, but it is annoying. I'm using standard GBI, and this has occurred with Sharp, Soft and Normal filters. I'm wondering if it's a problem with the configuration I can change somehow, or my monitor...