regardless of the height of the light, it's in their genetics to start flowering whenever. which is why they'll flower under 24hrs light but I've learned they really like that dark period so It's best not too. No matter what auto you have most of the time your yield is quit small, I've never got an amount that blew me away. I now only grow autos in between my regular grows to give me something to smoke on.
The light higher up will make them stretch abit more but Im not sure it'll change the amount of bud. Personally I'd be happy if I were you, I've had autos that didn't even flower and I had to switch to 12/12 light after 40 days to get them to start. just curious what kind are they? Also depending on the light you'll be loosing alot of usefull lumens keeping it higher up. The more lumens the better your nugs will be.
