Not all SA drmbrakes have out of the box good brake performance. Sometimes the brake pads have to be grinded lightly to allow full contact between brake pad and drum surface.
Also short brake cable routing with as little bends as possible ist highly recommended.

If this is done brake performance is very good.

SA drums are used in recumbent trikes and velomobile and are often due to above mentioned points not satisfactory ( brake cables are usally longer and with one or two narrow turns)