Curios to see how your twins will do .
What read about Autos is that 12/12 will take much longer will be interesting to see what you discovers.
I can say that mmy 3 auto short ryders lived in 12/12 from the beginning......they are a 6 to 7 week from seedlol......the first one harvested was about 8 weeks.....the other two might have abouut a week to two weeks left.....should finish up around 10 to 11 weeks from seed........now the weight i will pull off the last two will be close to what i got off the very first one i did aobut two years ago.....that was in a 3 gallon airpot......these are in 1 gallon airpots......i think 18/6 is optimal for autos, but 12/12 does work and seems to be comparable in weight....will know for sure soon......hope this helps........
Oh and Reg....i grew one of those auto afghans as well.....i did it in 18/6......my humidity over the summer stayed close to 60% or higher and she came through just fine so as long as your rh is below 60% most of the time then i think you should be fine......you have good airflow in there anyhow