I really like it too! I will probably put wire on the inside of the bottom wood panels, just because I am TOTALLY freaking out over predators! I'd rather be safe than sorry.
I was wondering the same thing if their little feet could get stuck, hardware cloth at that size would just be way too expensive. I have to do this as cheap and proper as possible.
You mentioned you choose to free range. I would love to do this, probably only when I am out there with them though, I have RA so running from the house all the way to the back yard to ward off a critter doesn't sound like it would do my body good, lol.
But I am curious, do you leave your run door open so that during their free range they can grab food (I know they're eating in the grass, so probably don't even worry about feed huh?) and water when they want? Wouldn't day time critters run in and try to wait until the chickens come back in? I wasn't sure how to do this if I let them free range with me out there.
Ooh! Sounds like you have little snake charmers! Ha! I was reading in another thread someone used minnow buckets (the wire enclosed containers with funnel ends) to catch snakes! He used, you guessed it a few eggs for bait! It worked wonderfully! Poor person had copperheads! I loved this idea and filed in the back of my head for future reference!