I've known about VPD seems like forever. Good info, but since I was an outdoor grower and had no control over the conditions, it was filed away in my brain with all the other superfluous info, like the minimum crush of the V-packing stack on the stem of the hull penetration of the gagging device for VH-1 valve(commonly called the "Mother's and Senator's valve") on a 688 class sub. LOL!
Since paying pretty close attention to control the environment for the optimal VPD level in my tent, I have noticed a marked increase in bud growth(swelling) rate and additional new growth and water usage.
I think this one detail will help me to grow better and bigger girls in the future. And it's all because of the great growers here on AFN!