Take an extra large piece of fabric, center it over the muzzle so there is plenty of fabric to grip between your finger, push the rb down into the muzzle, mark the muzzle on the patching with a flow pen, and then pull on the fabric to pull the patch and ball back out of your barrel. You can then measure the width of the patch as if you cut the patches at the barrel, and then choose the size you want for square patches without using a lot of extra material. With the .62 cal. ball, you don't have to worry about the extra material causing the ball to fly in different directions as the ball separates from the patching. The light weight of the patching compared to the weight of the heavy round ball is not going to be a factor in accuracy. I would think that the suggestion to use a 1 1/4 " patch leaves you enough room on the sides to not have to worry if you don't exactly center the ball on the patch when you are in a hurry.
