I did that before but mame would not compile . This is why I posted here
Do I change both or just the MDRV_VBLANK_DURATION line ?
This is the most accurate i have found
MDRV_FRAMES_PER_SECOND(59.1856)
MDRV_VBLANK_DURATION(DEFAULT_REAL_60HZ_VBLANK_DURATION)
Worked fine for me and fixes many sync issues in the intro's.