There are a few threads on the topic. Some have rewound an alternator for pack voltage charging. In most cases it's not worth it for the mile or two you might get back from regen.
He's getting about 10 amps at pack voltage. I can barely feel 10 amps of regen in my car, and it won't give you any noticeable range. For all the work he put in he basically ended up with nothing as far as I can tell.
And actually the video shows 177volts and a peak of 18 amps, so even more power than we calculated at 160V and 10 amps. Makes a bit more sense now, though I still doubt it does much for his range.*I suppose the rear brakes plus 10 amps of regen could skid the wheels in the snow.