It seems that some lessons I'm destined to learn over and over and over. In my excitement to begin work, I was not careful with blending the seams. The photo below shows a detail of an area where the seam is most apparent.
Because the painting consists primarily of transparent yellow, it is almost impossible to completely cover the offending scar with paint and clear wax alone. I painted a semi-opaque white wax, mixed with a tiny bit of yellow, over the seam. But I also had to add the wax over other areas of the painting, so that the resulting texture would be more unified.
I call this the ugly stage. It takes me a few days to actually build up the courage to attack the painting in this way. After applying the patch, I scraped it to a smoother consistency, and then started re-building the painting.
This detail of the area now has four or more layers of oil paint rubbed, painted and burned into the surface. You can see where the underlying wax was added, because the area is more textural, but I think it is richer and more complex than the original. It's a time-consuming approach which requires a lot of patience and trust. Check back later to see how the patch integrates with the rest of the painting.