Suggestion for scanlines effect with prescale=1?

[pmc]

Hi. My cabinet is running MAME 0.139 on an older 2-ish gHz Athlon XP with an on-board Nvideo GeForce 4 MX card. My display is a 21" VGA CRT.

Prior to this I ran an older MAME and had scanlines working OK for my tastes. It seems that to get a good scanline effect with 0.139 I should prescale by 4 and run at reasonably high resolution. But I don't have enough horsepower to pull that off without making games unplayable.

Games run great right now with ddraw and prescale=1 but none of the scanline effects look particularly good. I don't need it to be authentic, but it does need to look realistic. Anyway, I figure I need to make or acquire my own png to work better at this scale, but I'm not sure what my approach should be.

Suggestions?

Thanks...