Hi Jack,
Thanks, i've read it and i still don't understand.. there is no step by step tutorial and seems outdated.. i am missing something?
You're missing the required knowledge about CRTs. Without that knowledge there's no step by step tutorial that can help. When you know how a CRT works, VMMaker/GroovyMAME options are self-explanatory (almost). And, yes, the documentation is terribly outdated, but that's another story
Now, you'll probably get better results by just using the arcade_15 preset instead of the pal one.
You can export your adjustments from Arcade OSD back to VMMaker, and from there, to GroovyMAME:
Arcade OSD (make your adjustments, copy modeline to clipboard) -> Notepad (paste, get modified crt_range) -> VMMaker (edit monitor presets, replace the desired preset with the one you got from previous steps, mark export settings to GroovyMAME)
It's much simpler that it sounds.
Alternatively, you can copy a raw modeline into a game's ini, but that will only work for a single video mode, while using a crt_range allows applying the same adjustment to all modes.
Vertical centering works much in the same way as horizontal centering. Modify the relative size of vertical porches in order to move the picture up or down. Vertical size, however, is not adjustable by software.