Hey guys I'm starting on the adult coop for our silkies as they are currently in our old duck coop. I need it 20" off the ground so the birds can shelter under it and to stay above flood water here in Texas. Are pine 2x4s suitable or will I need to do full 4x4s to get proper support? It's being built out of fence boards so the wieght shouldn't be horrible but it will have a plywood floor and support up to 8 birds and roosts etc. Can I just do 4 legs as normal or should I have a center support on bottom to prevent bowing?