Thanks everyone. My points plate assembly is a Genuine Honda one. I was considering elongating the holes in the main plate to get more adjustment. I only need a fraction to get it bang on.
Wow, those appear to be TEC points, too: they are some of the better ones!
One thing that I think I can see (?) in the picture: is there a small gap between the upper ridge (lip) of the plate and the top casting (where the top screw holds the plate on)? If the plate is of substandard diameter, the points will push the plate downward with their spring force while you're setting things, and this moves the whole geomerty in a retarded direction. This "gap" used to be spec'd at not more than 0.1mm (0.004") maximum at one point (on any of the 3 mounts), but this spec is long since ignored. I have recently seen points plates with as much as 0.12" of 'gap' between the edges of the plate and the mounts. I've been setting curved feeler gages into the bottom edges of the gaps to center the plate while setting it up, then remove them when final-tightening the screws.
In one case, I had to push the plate all the way up to the top to get it to time up, but it had both substandard diameter AND worn points.