unwanted outlines

Hi all,
I've been having a heck of time trying to address this issue. I've made a little drawing patch using jit.mgraphics. The drawings are done with a transparent background. Each line that I draw, however, has a thin grey outline...basically everywhere in that layer where the drawing borders on a pixel with an alpha of 0. I've been told by the powers that the issue most likely is not with jit.mraphics, but the blend settings on the different layers. Currently every layer is set to alphablend (blend_mode 6 7). I feel like I've tried every blend mode combination, but it's usually been for all layers at the same time. Perhaps the answer lies in a magical combination of blend_modes with the different layers.

Here's the link to my original post on this in an mgraphics discussion:
https://cycling74.com/forums/jit-mgraphics-alpha-drawing-on-transparent-background

And here's a post a bit later with an example patch showing the problem:
https://cycling74.com/forums/jit-mgraphics-alpha-drawing-on-transparent-background

Has anybody run into this before? ...and have a "fix"?

Thanks in advance for any pointers.

Cheers,
David