Sounds like he’s towing the FR since an FSX 178BHSK is a travel trailer. Unless he’s pulling doubles…
So, towing with a Honda Pilot? I’d be very careful about staying within the the GCWR. The need for a transmission cooler tells me its already stressed.
If the Pilot is a 4x4 it can tow 5,000lb (according to 2018 specs) and the trailer dry weight plus max CCC is 4830. Add the WDH and you are getting very close to the max towing capacity. So it would be important to really watch the load and keep it at or under the published 1081 CCC. I like a little more margin than that.