The study that you cited there is for HIGH WATTAGE CFLs and their lumen output based on mounting orientation and AMBIENT TEMPERATURE. If you look at the range on the chart that is ideal for cannabis, which hopefully most of us are within, say 20c-28c, the deviation of lumen output is only around 5% different between the horizontal and base down mounting.

That all taken into consideration, I don't know if this study is even addressing low wattage CFL's like most people on here are using to grow.

Still want to see something significant about this.