How much height needed in my closet for 600w HID

About to start my second grow. I made a "closet" in my outdoor shed that is 2.5'x4.5'x5'. This wasn't a problem on my first grow as I went T5s all the way through and scrogged.

I'm looking to put in HIDs now and trying to decide between 400 or 600w. Is 5' too short for the 600w or 400w? Growweedeasy recommends minimum of 5' for a 400w but I wanted to see if anybody had first hand experience they could share.

Check out the recommended distance from canopy each light requires. Take that minus the size of your pot and that's what your left with essentially for room for plant growth.

Also check out cool tubes if you havnt already