Nah man, those things are matched to bulbs and its not cool to mix and match. I'm not saying it wont work but I wouldnt do it. I got enough to worry about without worrying about my house burning down for mix matching bulbs and ballasts.
as soon as i get another 400wtt mh i am going to try itin my 1000wtt hps. just to actully see what happens. i have one that dead maybe i should try that one. itwould be kool if it lite up.