While Mame32 is open...Right click on the game(pacman), properties, 'screen' tab, under view-choose cocktail...
Okay, understood. Didn't know mame32 had this feature.

I am more than willing to choose a different FE. Is there one that allows the in-game screen flipping between 1/2?
Nope. To repeat myself, it's done in the game (see changed to bold text on how to do it):
Mame and Mame32 won't flip p1/p2 unless the original game did it the arcades. Most games that flipped had a dipswitch between upright & cocktail. To get to these dipswitches, start the game, press tab, go to dipswitches, and look for an upright/cocktail dipswitch. (But as Dizzle said, some games do not have cocktail mode emulated yet even if they have the dipswitch.)
IIRC, there were variations of mame that recompiled mame so the cocktail dipswitches were changed to default to cocktail instead of the normal default, but I never used them. Sorry.
If you can't find the variant (or it's out of date), other methods include:
- Start all the cocktail games, hand change the dipswitches to cocktail,
- Edit the source so the dipswitches default to cocktail, and
- Find all the games games cocktail dipswitches and the needed stats, and make cfg/cfg files that change the dipswitch settings.
All three are "easy" but highly repetitive. If looking at the source in scr/emu/drivers (for #2 & 3) and the cfg files (for #3) doesn't ring a bell on what to do, I advise doing the first. If you try either the later, I'll help with basics on how mame works, but you'll have to do the real work.