I finally had some time to get back to this project.
holes drilled in the new swingarm:
I finally got to use this fancy tool. I've had it for years and never used it.
I made the shape in cardboard first, then aluminum
And then I welded it all up. It was difficult welding the section around the brake bracket due to the difference in thickness of the pieces. The brake seems to mount just fine.
And here's the other side finished. I later had to grind down the welds around the two chain-stay hole to get it to mount.
I weighted the swingarm before and after. These modifications added 13oz.