How big do you think I should go w/ 400w HPS and side lights

I was doing a 800w HPS (2- 400watts) and about 300w of side light. My space was 5 by 8, which I now think is way too big for just 1100w. At least, I thought so.
I'm wanting to down size and just use one 400w w/ around 200w side light.

How big should I go?
I have all the stuff I need besides soil and my box, so I am mostly prepared!


I was thinking 3 by 4 or 4 by 4ft?

Super Silver Haze and Blue Afgoo BTW. my lungs are looking forward to it

I ran 700w in a 2x4x4 with success along with a 388w in a 2x3x4 with good results. I think i would go with a 3x4 personally.