FYI, A Scanline Generator alone, isnt going to produce arcade accurate results. Thats merely the space between bars positions.
However, it does nothing to replicate lower dot pitch monitor displays, such as color bleed mixing, transparency effect, edge smoothing, glow leak, and overall color output differences.
If you have the PC horsepower, and willingness to spend the time in tweaking it...
you can achieve much more realistic results from the new mame monitor output settings.