useing a 150w hps in a 400w ballast

Can i use my 150w hps bulb with my 400w ballast? im pretty sure i can since its less wattss etc.. just wanna make sure--- my 400w bulb has not come yet do to shipping error.. and i got me a tent.. since the 150 is a complete one kit set up i cant keep my ballast outside the tent like i would want to... i would have 2 keep it inside... but if i use the 400 set up i can keep the ballast outside..??????????????

I see this is old but if anyone else runs into this it might work but I doubt its safe and it will kill your bulb quick and possibly overheat the ballast and/or bulb...if you wanna risk it, I wouldnt , sure you can put a turbo on a stock n/a engine and throw 40psi, but how long you think its gonna last?

Wow