Having grown various autos for several seasons now, I have found no reason to limit their light less than 24/0. I don't understand the premise that they need rest as theri little factories will run 24/0 if they have light. Mine have done well always and produce some good nugs.......having stated that, at times when I have too many in my "closet", I'll put a few outside or move'em to a 400w hps....Personally I have found little to no difference regardless.....
I believe cloning to be of no use as they do their photoperiod thing regardless of what you do.....I just let two of mine mate and got a shit load of seeds that I'm growing now which is a much better use of the plant......