I can confirm that the rattling I reported was caused by my current limiting circuit misbehaving (shame on me!)
After the servo speed/direction regulator came, it became real easy to deal with. Still, with no torque limit at low speeds, and with my low tyre pressure, I prefer the good solid stop that I constructed using two rubberized stops from an old hard disk and an aluminium plate bolted on top of the seat tube bracket. I’m riding the bike for several days now with no problems.
With one 6S 3AH battery, the total weight of the system is about 1.5kg. I’m mainly turning it on up hills.
Although my particular motor model was sucking air through itself pretty well, just for peace of mind, I used 50mm fan blades from an ancient CPU cooler for some additional cooling.
I couldn’t find a comfortable position for the button of the same type as Adrian uses. On flat bars, my hand feels uncomfortable wherever I place the button. Any ideas, folks? Right now I had to use the horn button from an electric bike (a few $ from Aliexpress) which works pretty well. I’m not sure yet if I will use the hall thumb throttle.
The next step is the Arduino! (wish me luck