Might be a silly question but does this work? I understand the other way around will blow the bulb but under powering a 600w bulb, will it glow like a 400w? Or would it just sit and blink because it isnt getting enough power? It is just i am getting a 600w light soon, and i will only need a 400w Sodium for one flower stage and i didnt want to waste the money on a bulb i wont use again if i didnt have to. The ballast is digital.