Cat Shield Trapping Heat Issues?

I've had my Valhallas Shields on for over 2 years, I was concerned about the heat build up since the truck spends quite a bit of time at the Ranch in the fields. So far haven't had any issues and I think they have enough ventilation.

 

This is a worry of mine, while waiting on my Valhalla order. I have a 19 without the external trans cooler. I just towed my 6000# travel trailer for two hours one way. My temp on Scangauge 2 averaged 217. 221 was the highest. I'll be happy to report any difference after I install the plates. I tried to get the oem cooler setup before the plates, but my wife wasn't interested in the $1000 price tag. I told her that she has to help me remove and reinstall plates if we end up needing the cooler.