600w dimmable ballast run a 400w bulb?

I have a digital quantum ballast thats 600w, Will it work to run a 400w hps on the 450w
power setting? Im not worried about life span as long as it lasts 12 weeks of flowering 12/12

Yes, it "should" be fine. Prolly will shorten lamp life, but should make it 12 weeks. You also might change the color temp slightly, but shouldn't make a huge difference.

yup^ i did a video with a 400w on a 600w ballast.
It's the Jd grow video on my grow thread.If you want to see it.

I've been reading up on this and I don't think so. You're never supposed to run a lower wattage bulb on a ballast.
You can run a 600 watt bulb and dim it to 50% or 75%. I'm not sure if you still get the right PAR or lumen output
proportionately but if you search:

"no unfortunately, the ballast are only designed to lessen the power on a correct wattage bulb, and not use a lower
wattage bulb if you were to use a lower wattage bulb on a higher wattage ballast it would pretty much turn into a
glass grenade and cause some serious damage. -Greners Staff"