Anywhere from 1 1/2 to 2 1/2 mm is fine. Mostly personal preferance. They can be made like the Lyman, in pieces but sewn the same, likewise but bound, or sewn inside out and turned. If you can view my facebook page (have not finalized moving to imgur from photobucket) at James Rogers - 18th Century Sporting you can see one I just made. It has a shoulder strap but is the same for the belt bag. It is based on two different 18th century English sporting images.
Rich, they utilized their pockets : )
I think shot and wadding was about all they carried in there.
Cleaning worm was usually attached to the ramrod.