FYI, Sturmey drums are designed for short-pull levers. You might get better braking performance initially with long pull levers, but you'll eventually damage the brake plates on the hub. If you move the action arm by hand, you'll see that there is very little distance between full-on and full-off; pulling extra cable won't help any. The ideal lever is an older mtb lever for cantis, or a bmx lever-- or very old dropbar road levers are good. Modern road levers have a little bit less pull than is optimal, but they're still much better for the S-A drums than a long-pull lever.
I've been running these hubs on a bunch of bikes-- some bikes are just a front drum with a coaster rear, but one of my bikes is drum f/r, as is my wife's bikes. They're strong enough brakes, but they surely ain't discs. They're super underwhelming when new, but once the pads and drum wear in, they're pretty danged good. (An advantage to these hubs is that the pads last forEVER, but you need to readjust cable tension periodically as they wear....) Best way to set'm up is to dial in the cable tension to where the pads just begin to drag, then back off a tiny bit. Too much slack in the cable, and performance suffers.
HTH
-Rob