Rule of thumb I follow is clone for sex 3 weeks max Earliest I've had is 11 days I have been able to Identify. T5's definetly show sex w/ pre flowers w/ 24 hr but definitely under 18/6. Usually males grow larger then females IMO. I would never throw or destroy a plant for sure till sex is 100% determined... I had a couple of times were I almost chopped and said ahh give it just a few more days and pistols Popped... IMO Males show sex sooner but then You need to wait for the females anyway... Normally 60/40

Good Luck GL1