I have shot .575 balls from my 20 ga type D Fusil. I used denim patching, cut from the leg of an old pair of jeans. Never measured the thickness, I'm going to guess it's somewhere around .025". Used 65 grains of 2F goex. Fairly easy to load and accuracy at 25 yds was pretty good.
I have since purchased a .60 mold. Those balls, I shoot with 0.15" commercial patches, prelubed with wonder lube. Harder to start into the muzzle, but go down pretty easy. Accuracy is better than the .575 balls.