To answer your earlier question about number of cells, the answer is 24. The paralleled opto outputs don't seem to be an issue, all seems o.k. at the moment.
To answer your regen concerns. I could still use the clutch pedal and a hall sensor, but I chose the simple route. The Kelly controller has programmable limits for over and under voltage of the pack. I have set these to 86 volts and 60 volts respectively. It will start to reduce regen and drive output as required when it gets close to these limits. That with your slave boards connected to my management module which will also cut regen completely (or drive after a 5 second warning) if any cell goes over or under voltage, should keep everything happy.
The Fiat is fitted as standard with drum brakes all around. There is quite a lot of travel before the brakes actually apply, so with the brake switch adjusted correctly you get regen without using any braking and for the last few feet when coming to a full stop and the regen cuts out due to slow motor speed your foot is already on the brake.
Thanks for your concerns, it keeps me thinking about why I have done something and sometimes makes me reconsider choices I have made, keep your concerns coming.
It's like a Mexican wave 
