I recently came back to this, having reviewed the links from Janey, and letting it roll around in my head for a while. I rechecked the needle bar height, for starters, and tweaked it a little a bit. While I was at it, being a person who likes things straight and being the smartest (and only) person in the room, I eliminated the annoying slight cant in the needle bar. Turns out, further along in the service manual, that annoying slight cant in the needle bar is supposed to be there...so much for being the smartest guy in the room. I checked the timing after adjusting the needle bar height, it was off-a little behind, actually off before I adjusted the needle bar. Not sure if I did it incorrectly the first time. So I corrected that. I ran a bunch of stitches as in the pictures. The top stitch always looked fine, the bottom not so much. In one of Janey's links the person had the timing advanced slightly, so I tried that, not much change. Someone else had suggested bobbin thread tension, so I was adjusting that also, only an 1/8 of a turn at a time, which made a lot of difference surprisingly. I finally settled on leaving it as is and if I ever zig zag with it, it won't be much.
I did learn one thing, something true VSM veterans have probably been doing all along. I loaded up test bobbins (class 15s and 66s) with bright green thread, bright orange for top thread, I bought needles with known sizes for different test fabrics, instead of relying on eyeballing needle sizes from the catch all container. Unfortunately the people at the fabric store didn't really understand what I was trying to do, set up a test packet including different thread sizes for different needles, so I ended up with all purpose thread (I couldn't discern much about thread sizes from the 12,000 spools I was looking at).
But now I'm ready for the next machine.