Im considering getting myself one of these 300w ufo led's. grow space is 120mm x 65mm x 55mm. now i read that over 300w, led's should be kept 60cm away from plant. So taking pot size and plant height in mind, i will have to extend my grow cabinet with roughly 40-50cm giving that pot + plant will take up about 80-100cm. is this correct, am I on the right track here?