In my grow, I use 4- T5- 2' bulbs that are "desert 50" normal output, 14w each, but I use a IceCap 630 ballast to drive them to VHO levels, 40w each. Bulb life is shortened but output is very much increased. I use this supplemental lighting only for a few hours per day, during the middle of the photoperiod.
I just started using a HO T5, 2ft, 4 bulb, 24 watt, 6500k bulb fixture...:thumbsup:

I use this for 3 weeks...before transplanting and stepping up to 400 watt CMH.