Kate MOSfet

Hi! I'm up to constracting a similar UV exposure box in order to print photos with the cyanotype method and other alternative printing methods. My problem is that I need to use UV emitting lamps(Phillips Cleo Fluorescent) of 40W and I don't want to use a ballast for each single lamp. Is it possible to follow your diagram and use a ballast of 80W for each two lamps or this would be a problem? Thanks in advance