Cool bike!
I hope you replaced that zip tie on the drum brake. There's a tremendous amount of force on the arm while stopping, and it'll break that easily.
I tried a stainless hose clamp for the same reason you did, and it snapped at the first brake pull.
An atom drum snapped a steel bracket on my motorized bike, spinning the bracket and locking up the front wheel at 45mph.
Broke 4 ribs, wrist, two fingers, seperated my shoulder which required surgery, and bruised my heart, lungs and kidneys.
So, yknow, just sayin'...