I am not a good enough shot to prove this out for sure, but it comes from some very good shooters and I believe it based on my experience. You'll generally see better accuracy the tighter your ball/patch combo is. You may need a short starter and to smooth out the crown with emery paper to prevent cutting patches when loading. If interested, I can send you a link on the instruction.
If there's a Joann's near you, find their 100% denim, take a pair of calipers, and measure the thicknesses by squeezing the top and bottom jaw together as hard as you can just using your thumb and finger on one hand. Their thickest, which I think might be 12oz, comes out at about 0.022 ish for me. That have some called bull denim that is around 0.020ish. These are great, very tight weave, and durable. They work really well for me. The duck canvas also works well and is about 0.020. Anything you get, wash it with soap once, rinse twice , and dry on hot to wash the sizing out.