problem with direct3d scanline effect / .cfg settings

[brandname]

i'm using a wg d9200 monitor with a generic video card (still afraid to install arcade vga) and am trying very hard to achieve a full screen scanline effect WITH hardware stretching turned on.

after lots of playing with the mame.cfg file and some online research, i SORT OF got it to work using these parameters (using mame-wah and command mame)

-direct3d:  on
-hwstretch: on
-cleanstretch: auto
-resolution: auto
-zoom: 2
-d3deffect: scan25

i say sort of because when i fired up ghouls n ghosts it worked great...  however, when i switched to donkey kong, the screen was non-interlaced and very very small...  i discovered for most games this config. shrinks the video screen by 300% and has no scanlines to speak of.

can somebody help me out, i have everything running so smooth now (no out of range errors, smooth horizontal synch) i don't want to ruin the GOOD settings i have by guessing

thanks!
patrick