All the comments you read on the BYC about watching the chick behavior to know if they are comfy, cold, or hot are so true. I took out the thermometer probe last Friday because there was no need for it anymore. You will pickup real fast on whether they are comfy or not. Your box looks good!
I've been setting up my portable coup for their move outside. I let them spend most of their day outside over the weekend. They appear to really love it. Flying around, running all over, scratching.
One note: I have been using a quart mason jar feeder, with the little 8 holes in the galvanized base. so when I put them outside I filled it up all the way. when I came back to check on them about 2 hours later, the jar was empty. They had somehow scratched it all out onto the ground. So now I will only fill the base up when I set them out.