I'd have to agree with PJ in that every rifle is different. The most accurate ML rifle I ever owned had a .45 Getz barrel. I ended up using an unbelievably tight ball/patch combination and nearly 80 grs of 3F Goex. Other rifles would chew up the patch if I tried such an oversized ball. I've tried double patches, and even super thick single patch material with lighter balls, with varying results. In my experience, I've always had better luck with a single patch of regular pillow ticking, then varying the ball size or powder charge until I got the accuracy I wanted, but you may have different results.
Kind of changing the subject, but I've also noticed that I shoot differently now, too. When I was younger, I got better accuracy with heavier charges, but as I've gotten older, I've found that I get tighter groups with lighter charges, even using the same rifle. I assume it's because I'm holding my rifle differently. Right now I'm using a .495 ball with ticking from the local fabric store in my hunting rifle, but that might change down the road.