So I've finally found a 400x254 modeline that works great in Arcade OSD on my WG 4600 arcade monitor (8.18 400 416 456 520 254 262 265 288 -hsync -vsync). But when I actually run Rampage World Tour on MAME, I get wavy lines as in the attached JPG.
I'm running GroovyMame on Windows XP (MAME 0.171, SwitchRes 0.015m, ArcadeOSD 1.4). Any ideas why it would work in Arcade OSD but not in MAME? Is my mode (400x254 @ 54.621) somehow not close enough to the resolution MAME wants for this game (400x254 @ 54.706841)? If so, any suggestions for fine-tuning?
Thanks!
EDIT: Note that bumping the dot clock up to 8.19 (for a final refresh rate of 54.688) didn't seem to improve things.