I also agree with the thinner patch, bigger ball theory.
I noticed I lost accuracey when I purchased Wal-Mart pillow ticking, (washed 3 times), and started cutting my patches at the barrell. Although the combination was difficult to start,(I don't know the thickness of the ticking) with .495 round balls, it was the tight fit we seek. Accuracey fell way off.
When I switched back to my thinner ox yoke pre-cut patches with the same ball, (.495) it was much easier to start, AND my accuracey improved which was a bonus.
So, my next experiment is to try .498 round ball with an ox yoke pre-cut .010 patch.
I also noticed that the ox-yoke patches have a tighter weave than the wal-mart ticking, IMO.
Simply observations to ponder. Skipper