You can control the light. You can install an electric baffle for board rooms or home theaters. If the cost for the electric ones are crazy I could install a manual shade or something like that.
I was also looking at light meters :
http://www.testproducts.com/safecart...roducts_id=414
That one has an RS-232 output so it can be hooked up to turn on MH bulbs on cloudy days as supplemental light.
I know someone with one of these in their bathroom. It's extremely bright. I may buy a light meter (off eBay for now) and see if they will let me take the diffuser off it and get a reading when the sun is out and again when it's cloudy. That will give me a better idea how much light comes through them. The manufacturers claim as much as 98%.
Even if I still have to run MH bulbs all the time it would only be supplemental and not close to the amount I would need without them.
I think I have pretty much sold myself on this idea but would love to hear from someone who has allready tried it or seen it done. LOL