I have another concern about the sod for your ferret pen. The bottom layer of sod is a plastic mesh. This mesh is like heavy fishing line woven into squares. If (when) the ferret digs, it could become entangled. A ferret might look at it as something to eat. A friend lost a wee one years ago after he ate beading string. I have adopted Desert Tortoises. Their yard area is half sod. Last summer one female decided to dig the sod and got the mesh tangled around her legs. I expect a ferret could run into some problems too, I know you will want to watch closely. Your play area sounds just wonderful. Ardith [Posted in FML issue 4916]