There are some that say don't top autos and there are others like me that do. I usually top around 4 weeks or a little later just as she starts to push out some white pistols. This usually gives you 5 leaf nodes and top there. I Low strength train my plant as well and I have broken the top off while it has been in flower for a while and I don't see a higher yield.  I top at 5th leaf node up at 4 to 5 weeks and I see a lot of extra growth. If it was me I would not top because it will add more time to finish and in my opinion I don't think it will increase your yield this late in the game. 

Would like to know breeder and age. Just for my own curiosity. :)

Welcome and Happy growing.