To check that, there are a couple considerations.
First, fire up your HPS over a clean floor and make note of the light distribution. Is the light intensity and spread roughly the same on both axes? Ideally, it should be.
Next, are you running an air-cooled hood? You will want to arrange things so that the flexible duct coming off your hood will never get entangled in power cords or hanging chains. Personally, I'd have my duct sticking off the SIDE of the thing, facing the wall to which my blower was mounted, and leaving a slack length of duct between so that even at the ENDS of the light rail, there's still not any tension on it. Be sure to use hose clamps/straps instead of duct tape in this situation, because no matter what, it WILL tug slightly, even from the weight of the ducting. A string tied around the ducting about halfway between the hood and blower and then attached to the ceiling to take some weight will help though.