So I only have a few grows under my belt and finally have enough space to do it right. I actually have more space than I need, so Im wondering if I should build some temporary walls to keep the plants and light contained? Based on what Ive read I should have an area of about 24x24 up to maybe 34x34 to get the correct lumen per sq. foot ratio I have a 400 watt hps. So should I just use the reflector with my cool tube to focus the light on the area I want? Or should I put up some plywood/foam board walls lined with mylar around my grow space to reflect the light that would otherwise be wasted back onto the plants? I have a fan and ventilation so heat shouldnt be a problem. What size area (footprint) would most people recommend for a 400 watt hps if Im more concerned with quality than quantity? Eventually Ill get a bigger light but for now just looking for input using what I have. Thanks in advance. PS I have 8 feet of vertical space to work with.