That is not the best pattern, you should try get it better, but sometimes normal wear will distort a proper pattern. If you go one way with the pinion and then back the other and it gets worse that may be the best you can get. I am not a gear expert I have only done about 10-15 setups. Most of the time you can get real nice picture perfect patterns. The resaon I responded is that I had that exact pattern in my 9" when I rebuilt it a few months ago. I took out shims and set back lash it got worse. I added shimms and adjusted backlash and it even made noise turning it by hand so after a full day of trying everything I could and much digust I left it with the pattern you have. Funny thing it was the exact shims that it came from Ford with. It runs quiet and cool.
I had the same problem as you are having with the varing backlash. The original Ford Manual says to set backlash between .008 and .012. The maximum variation in backlash arround the whole circle is not supposed to exceed .003. Ring gear runout is not to exceed .003 also. You are exceeding the backlash variation.
Here what I did because I am cheap not becuse it is right so no one flame me. I had no measurable ring gear runout when measured on the back of the ring gear. Obviously the problem was in the cut of the ring gear or possibly wear from runnot caused by the carrier I replaced?? Or possibly and I say this based on years on dinking with ford products (again do not flame me or I will send you a very long list of crap that left the factory way out of spec), It left the factory that way and ran 70K miles with no problem. Could be the pattern problem?? So in my cheapness I decided to set it up so that at my tightest backlash I had .008 (do not set it lower) and at my highest backlash I had .0013. I got the best pattern I could with that set up. Yes it took all day and the final pattern looked just like yours.
I am not happy with it. Even once it has 100K miles on it I will still worry that I should have just got another gear set and not been so cheap. My father was a greyhound mechanic in the 60's. They threw things together to keep the buses on the road. He always laughs at the convolutions I go through worring over patterns. His opinion is if it is quite it is good.
Once upon a time I had a 55 chevrolet with a 4.10 R&P. Very bad wear from the PO running it without oil. Close to the same design as the 9" only much weaker. I could not get it close. All the experts said the throw it away but the 4.10's were hard to come by (cheap anyway) so I decided to put it together the best I could and run it. It howled like a dog. Took it apart and adjusted it to the best drive pattern I could get, while ignoring the coast pattern. It was quiet in drive and howled in coast. Ran it behind the inline six standard tranmission for about 60K then put in a hopped up 350/700R4 Corvette TPI and ran it another 120K. Never had a problem, Pulled it apart twice and checked my magnet for abnormal metal wear. Never had a problem other than the howl in coast. After a while you learn how to drive it to keep it quiet.;D
If you are still with me check the ring gear runnout, and decide if you are cheap like me and willing to take a chance or if you want everything to be perfect and by the book.