What we chose to do was to install the hardware cloth on the inside of the chicken wire on the frame. I'll try to get some photos of this to help explain it. Initially, we were going to just layer the hardware cloth over on the outside.
Issues:
1: By installing on the outside, it would be visibly obvious that there was an added layer. We have gone to great lengths to make this "look good" and put up framing around the outside to finish it off. I didn't want to disassemble the whole deal, as I wasn't sure how fast we could get it all back together and today is such a lovely day for my babies to be out and about...I'd hate to have them "cooped" up! haha
2: Installing on the outside over the other wire, but not enclosed by frame means that an edge will be exposed somewhere. If we are specifically trying to eliminate raccoons as predators (or slow them down a bunch), their little hands have enough dexterity to grasp the wire and pull.
3: If the larger holes are on the inside, I was concerned that a chick could try to pop through a bit, then get a leg or neck caught between the layers, panic, and OUCH!
Instead, by installing on the inside:
1: The chicks are now at least 2 inches away from the outer wire layer. They can't really fit any parts through the hardware cloth, and there is an increased "reach distance" for anything trying to get them. Hopefully, the time it takes to get through to the second layer with the hand tips off the chicks to danger so they can move away or head for the coop.
2: The predator must get through one layer of wire before encountering a second, tougher layer. The hope being that it will be too much trouble or effort once they get there. Also, all edges are able to be tacked up inside, so that nothing can grab and pull...unless the chicks try hanging on it from the ceiling. lol
3: You really can't see anything until you're right up on it, so the look remains as everyone wanted.
When it is cooler in the evenings, we will definitely be locking everyone in. The coop itself is very secure, with hardware cloth inside all openings to keep the chicks in and everyone else out. All doors have strong locks requiring two hands and some effort.