Below is the arcade_15 range line. The bolded values for HFrontPorch, HSyncPulse, HBackPorch respectively, and you can find them in ArcadeOSD when editing. Your values will be different, remember. Copy your values into mame.ini (or into each machine.ini - like neogeo.ini - or game.ini - like sf2.ini - if you need to for each game)
crt_range0 15625-16200, 49.50-65.00, 2.000, 4.700, 8.000, 0.064, 0.192, 1.024, 0, 0, 192, 288, 448, 576
You can also set these range options in VMM using the monitor.ini file by adjusting whichever line, like "arcade_15ex" as you note. But this way only fixes things once, you may still need to tweak individual modelines for individual machines/games. It's definitely worth exporting your modelines and keeping a backup off the machine somehere, and saving your mame config too!