I downloaded free plans for a pvc poultry pen ( http://www.pvcplans.com/pvc-pastured-poultry-pen.htm ) Anyone out there built this design? Here are a couple of my concerns/questions. 1) Is it heavy enough to not blow away (I know chickens fly but not in their cage ) 2) Do you use wire on the bottom? I'm going to use this for Cornish X's and we all know they make a heck of a mess. 3) If you look at the plans there is a box in the middle that they call a feeder. Huhh? Any other thoughts before I embark on this idea???