I was thinking of doing a cool tube for the light and venting the air from the seedling/veg chamber up into the flower chamber and on out. This will give the flower chamber some needed heat when the light is off during 12/12. It will need it as the temp here is already in the 40's at night and with vents in the sides and backs of the frdge, it will get cold in that flower chamber.
So cool tube for HPS light, intake vent at bottom of veg chamber, another outtake vent at top of flower chamber, should work. I will put a fan in top of veg chamber to pull out the flouros heat and put it into the flower chamber when the light is off. I have made a homemade darkroom louvre to keep light out of the flower chamber. I think this is an ingenius way of dealing with the heat from the light (cool tube) seperately, and using the heat from the veg chamber to keep the flower chamber at steady temp. I have noticed that two or three unvented flouros make a space the size of the veg chamber about 90 degrees or so. A small fan at the top of that chamber, pulling in cold air from the bottom vent, should maintain a cool nice temp in there and still keep flower chamber cool. If not, I can always add another vent at the base of the flower chamber.
By the way, I have a few little seedlngs going strong under one 100 watt cfl. It is slow going but I am not in a hurry right now.