The boxes get very warm ad so does the TV, do not place anything on top of the box. But you can do what I do, I place a couple of blocks under the box so it can get better air flow;-)
As for it catching fire it wont, but you did good by checking with us on that if you aren't sure.
they do get extremely hot but not enough to cause any fire hazard unless you have something blocking the top vents.
I hope this helps settle your mind?
In any case, I will stick with you until this is complete.
Please rate my service kindly.
Also it is the only way I am credited for my time and expertise with you.
Once you rate, I will be notified and will add your question to my priority list so you can reach me anytime until this problem is solved.
Then you can reach me by simply replying to this message anytime.
Thank you Gillian and have a great day!