As far as I know most people do not put ballasts inside their canopies, too much moisture due to evaporation. I would try to put them somewhere else on the outside of the tank or in your stand. Especially, MH ballasts and VHOs because they are usually rather big if they are magnetic. I guess you could mount the ballasts to the outside of the back of your canopy. You could also mount them to the wall behind your tank.