Samsung UN46C6300SF (1080p)
Snes mini with rgb amp and HD retro vision cable
Ps1 games via ps2 slim over component cable
240p passthrough: good
L3x: acceptable (see below)
L4x: acceptable (see below)
L5x: needs work (see below)
L3x and L4x will work after making the recommended adjustments from harumph, however, I cannot get the correct aspect ratio. Reducing V. Active back to 240 results in picture loss. I have adjusted every setting on the TV I can find and am unable to restore the correct aspect ratio. So Lx3 and Lx4 have a black border all the way around the image.
Edit: I managed to get line 5x working with some serious tweaking. Picture is extremely sensitive and becomes unstable very easily if the wrong timing is tweaked but I did get a stable image. Like Lx3 and lx4 it does not have the correct aspect ratio and any attempts to change it results in picture loss. Also there is a jagged pink line down the middle of the screen in this mode only. Changing back to L3x or l4x makes the line disappear. The picture you get looks stunning though and if the pink line could be removed it would be the ideal setting. I tested l5x with an rgb amplified ntsc snes mini over the HD retro vision component cable.