I haven’t testet it yet.
“X (Horizontal) Resolution: variable, maximum of 565 (programmable to 282, 377 or 565 pixels, or as 5.3693175 MHz, 7.15909 MHz, and 10.738635 MHz pixel dot clock) Taking into consideration overscan limitations of CRT televisions at the time, the horizontal resolutions were realistically limited to something a bit less than what the system was actually capable of. Consequently, most game developers limited their games to either 256, 352, or 512 pixels in display width for each of the three modes.
Y (Vertical) Resolution: variable, maximum of 242 (programmable in increments of 1 scanline). It is possible to achieve an interlaced “mode” with a maximum vertical resolution of 484 scanlines by alternating between the two different vertical resolution modes used by the system. However, it is unknown, at this time, if this interlaced resolution is compliant with (and hence displayed correctly on) NTSC televisions.
The majority of TurboGrafx-16 games use 256×239, though some games, such as Sherlock Holmes Consulting Detective did use 512×224″
So Floob should be right and the SNES Overlay should work.
I will test overlays tomorrow or the next days ;-)