That makes a lot of sense of things. Tweaking advanced timing to change 720 to 704 fortunately does work with my monitor, but that does seem to require increasing horizontal backporch in order to re-center the image. Is default +8 the correct value for the backporch in that scenario?
So if I use 3x or 4x for 240p (or mess with advanced timing for 5x) and adjust horizontal active and backporch for 480i and 480p, I can get the correct aspect ratio for 240p games and widescreen 480i and 480p games, but I’m still stuck only being able to display 4:3 480i/p games as being 10% too wide, unless I get a new monitor. With a bit of research, I’ve found that Asus, Dell, Samsung, and ViewSonic make monitors that provide 4:3 distortion as an option, but a new monitor seems like a big investment over a small error. What would be more helpful is if the OSSC itself had modes for adding blank pixels to the left and right sides of a 480i or 480p signal, just like 240px3 in generic 4:3. I tried achieve something like that using advanced timing, but I didn’t have much luck. Perhaps this is something I should post about in the “feature requests” section?
One last thing that seems curious to me is that the 240p optimal modes seem to operate around a different set of ideas about how aspect ratio should be handled, at lest for a 240p source. These modes seem to be designed to completely fill a 4:3 frame (or alternatively 8:7 for 256×240), but using the 240p test suite on the Wii, I get a narrower image in 3x and 4x generic than when using 320×240 optimal. If the optimal modes mess up the intended aspect ratio, that’s a bit of a shame, considering how fantastic things look with optimized settings.