OK I got it working pretty well. I tried the 320x256 @60hz mode, with vsync on, but (as I kinda expected) the games were running too fast (most noticably the music was waaay too fast). In the end, switching to the ArcadeVGA's 352x288 @51Hz mode gave me a much more "closer to 50Hz" experience. OK so I have tiny borders around the display area, but you don't even notice them really.
So in short, I set the following options (WinUAE 1.5.0, using ArcadeVGA2 [PCI-E] with a Hantarex Polo/3 arcade monitor): -
gfx_width=352
gfx_height=288
gfx_width_fullscreen=352
gfx_height_fullscreen=288
gfx_refreshrate=0
gfx_autoresolution=0
gfx_vsync=true
gfx_lowres=true
gfx_lowres_mode=normal
gfx_linemode=none
gfx_fullscreen_amiga=true
gfx_center_horizontal=smart
gfx_center_vertical=smart
All works a charm. Cannon Fodder never ran so great!

Doesn't seem to stretch the display either, which is nice.
Cheers
