Wouldn't you like to pull an extra crop per year (8wk cycle) from your HPS? In a small space (1 m^3) I can get 25-30k lumens from a 4' six bulb T5 unit. If I wanted to do it right I would change the light spectrum, but that becomes one more hassle. I'll probably try it out but it won't be for a couple months. I would love to hear if anyone has experience with something like this, or using MH in similar way.