I would definately go with the 48" lights as most 75's are 4'.If your really want to use N.O. flourescents(strip lights)I'd use no less than 4 and drive them off of an electronic ballast like an IceCap.They burn much brighter on that ballast than on the cheap ballasts that strip lights have..You will also be able to upgrade to VHO's without having to change anything but the bulb(the endcaps are the same size,VHO and NO are T12's).IC ballasts will fire any flourescent(NO,VHO,T5,or PC) in any combination.