Autos just don't perform that well outdoors in my experience, no matter what you do, they are really designed for indoor growing at 18/6.
It is the weeks of 18 hours of light each day that gets the size into them.
I agree too, best to just let them do their thing outdoors, with no topping or defoliation at all, but LST is fine.
Autos and outdoors = disappointment in my experience, just not enough daylight hours at normal latitudes.
Stick with much superior photoperiod plants outdoors would be my advice.
Cheers, Organoman.