The instructions are what I posted first. This was a trick I heard from SkunkmanSam on Hash Church.
The second post is what I ended up doing. I flipped only because I have height limitations. Some did start showing pre-flowers, as any sexually mature plant will do. Righ around the time they start alternating nodes…
No, sorry my english. I take your context in count and to sex them in the cups directly seem to be the most strategic move, considering your needs.
About the stress, an hydric stress in these cups is far more high than sexing them in the cups. It was to “relativist” your concern about stressing the plants.
I understand now. Thank you! 
Thanks for clarifying. I was 90% sure that’s what you meant.
12 hours of dark will begin at 6pm today, then they’ll get the same again tomorrow. This will be an interesting experiment. 
A female plant will present pistals while still very early in the vegative state. In general a Male will not present the pear shaped nodes at the base of the stalk of your babies. An 18 and 6 light cycle should be maintained. Stressing your plants is a poor way of sexing them.
Ok, Im going to try this too.
This is a victim, er, ah, a test subject in my HPA trials. It was a seed I won in one of the contests here on OG, but I have no idea which one it was. Somehow, some of my seeds from different people got mixed up and several got smashed. This is one of the few survivors. So I have no clue what it is - indica or sativa or a mix? Thats why Im using it as a torture, er, ah, I mean test subject
This is how it looks today.
I hope this is mature enough to try this. We will see
Maybe a little young, I’m counting five nodes, but I think @cogitech saw no stress from the two extended nights. I’ll be doing this with my Cherry Tart soon as well.
I love how open this community is to experimenting with different ideas. 
Still no signs of sex organs. Males are supposed to show first… Maybe I have all females. I doubt it, but stranger things have happened.
Hasn’t it only been 4 or 5 days? Should take a week or so, here’s hoping it works for you. 
Yep. It is still early, I guess.
The plants sure are happy, though. Will post some photos later in my conservatory thread.
No, they are his (Cali-O x Durban Tai High Flyer) x Durban.
my apologies, i think I was referring to the post by @anon32470837 where he said he got seeds mixed up and didn’t know which one it was.
No worries. I had 1 too many brownies last night so I’m a bit slow today…
Probably an old wives tale, @cogitech. I re-pot in Flowering occasionally and it doesn’t seem to hurt. They usually don’t skip a beat. I do this when I know the plant will turn into a giant, I’ll leave it in a small pot for about 3 weeks. They usually immediately hit a growth spurt for a few days and then stop.
Also, I don’t put them into larger posts until they have 5 nodes. I’ve waited longer some times. It seems that they show within a week of up sizing their pot.
That’s another thing I’ve found in the past. If I have no insect problems, my plants always look awesome after one day in Flowering. If I have a plant that is not looking as good as it should, I put into Flowering early and leave it. I think the plants are getting a photogasm from the 12/12 under the Flowering lamp. 
I like that tip, @ReikoX. 
I’m putting it in to my Grow Journal database so I don’t forget it.
I must be misinterpreting your statement. I find that, on average, the male seedlings present their sex 1st.
BALLS.
Yes, some of them are starting to show!
Will give them another day or two and then do a full assessment.
Cool!! Well, except for the BALLS part
So, it looks like it took 7 days from the day you started the 12/12. My baby just finished its second day of 12/12, so I have maybe 5 more days…
Yep. Pretty much.
Some strains are showing sooner than others. For example, I am 100% sure both my Pineapple Expresses are males, not sure at all about my two Northernberries yet. The rest I am fairly sure about, but not 100% yet.
Dispatched the two Pex males this morning. There was absolutely no doubt.
I am not 100% sure on the rest of them yet, but it appears that I might only have one more male in the whole group.
Nice to have lots of females to choose from, but it actually looks like all 4 of my CBDream x Critical Kush are going to be females - which is sad because I wanted at least one male so I could back-cross him to his aunt (the female CBDream).
