I've been playing around some more with that Mitsubishi analog presentation monitor. First off, I got some pretty good S-video. Not great, but playable. Does depend on the card, though. Now to the main reason for the thread.
I had snagged the computer I'd set up for my candy. It has an Nvidia MX440. Really weird, but it runs Advancemame just fine with my digital presentation monitor. Totally loopy with the candy monitor. I thought it was the composite video. But it also runs weird on the analog Mitsu, except in this case it runs double-image. HM.
So tonight I snagged another computer, same make but different video card, an Nvidia Ti200 and it ran Advancemame just fine on the Mitsu. In fact, it displayed vertical games at 60hz really nicely. Maybe because it's analog, it doesn't have separate modes, just a bandwidth of 15-36khz.
Here, the geometry is set for 336x240 (or maybe 288x240), so of course Bubbles fits just fine. And generally any game that ends in 240 will, too. Yet I was surprised that various vertical games run horiztonally had very little overscan. (First four images - I don't know why two of those are blurry.) But even Moon Patrol and Space Panic almost fit. The power of Advancemame, I guess.