Ok,I've been here before.First thing to consider is do you hope to achieve fat dense colas ,or would you be happy with smaller less dense nuggets?If big colas are what you're after,then ditch the cfl idea.They just dont put out the intensity needed for big buds.you need hid light for that like...
These were from my last grow in a homebox xl tent with a 400 watt cooltube.The last pic is from the previous grow in my 2'x3'x4' tall box using the same cooltube.The first pics are white rhino and the last pic is a blueberry scrogged.peace.
I think if you can get another 10inches or so of height in the bottom chamber you might be ok.30 inches of flowering area height aint too much for a 400 watter.also what temp is your flowering area with the light on?try to keep it at 80 or below if you can.
6" inch duct fan pulling fresh air thru htg cooltube, 4" inch duct fan pulling thru an 18" inch carbon can mounted inside the box. (4) 2" inch pvc elbow "inlets". works excellent temps 70 to 85 depending on ambient air temp and no stinky:hump: also have co2 monitor/controller but no tank...