The clutch handle that came with my BGF kit works quite well...
That being said, I don't use it.
I kill the motor if I must stop for more than a minute.
IMO, the mechanism is not designed well enough to run for any extended period with the clutch dis-engaged. It would either be grabbing a bit, here and there, causing it to heat up, or adjusted so that it would probably slip, once it was engaged.
My little Mighty 48 has always re-started very quickly, in traffic.
Actually, I attempt to judge the lights and adjust my speed to get through the traffic without stopping for each light.
I always think it's silly to see people racing from light to light, going fast as they can, only to brake heavily to stop, for every single light in town!