new veg room please help

So i have all of my lights and fans for my veg room and my buddy is giving me 20 ak 47 clones in 2 days. I have to complete my veg room so i have a place for them. I am using a spare bedroom for vegging and plan to build a simple box for them. There will be 2 400 watt MH lights and 20 plants. I will veg them for about a month or until they get about 2 feet tall. What size veg room would be good for those lights and number of plants? also any other input on what to do would be great. I was thinking of building a frame to wrap the panda paper around should i use PVC pipe or wood? THanks

rough 20x20 figure that the buckets will be one foot in width so about that