I do not have a cool tube :-( I decided they were a bit pricey all in all, together with a new fan etc,  since the future probably is LED. I will use an old 400w this time anyways. 

For my next grow I was thinking about flowering them in the middle of a 16m2 room with the 600w and keep the young ones inside the tent. I thought perhaps the 600w wouldnt be that much of a problem in such a scenario?