The SA brake needs to be adjusted until it just barely ticks from drag a little. The drum shoes and cable work in and then you can adjust it until there are no high spots or drag. That’s what I did anyway. It will work a little better after awhile, but still very weak. I guess you didn’t believe my earlier post when I told you they were weak. Be careful tightening the axle nuts, these axles strip easily, unless they made improvements in the last 8 years. I think vintage reproduction motorcycle levers might improve your braking, but you need to make shims for the bicycle cables to fit on these levers. Motorcycle cables and barrel stops are much bigger than those on bicycle cables. Perhaps try long and short pull bicycle levers to see if one works better. I don’t recall which levers your supposed to use with it. I think short pull have more leverage. Usually if something pulls twice as far you end out with half the mechanical advantage and have to squeeze the brake lever twice as hard for the same leverage. I’m probably wrong, been a long time since high school physics. A drum does allow you to ride corners faster and helps keep the coaster temp down. Don’t touch your coaster after a big downhill ride, you could cook hot dogs on it. How about some pictures?