First year putting up foxes. I have been trapping a farm managed for waterfowl and the foxes I have been catching have been loaded with fat. I flesh them pretty good but they won’t stop sweating. I whip them down everyday have fans and a small heater going . Could I give them a light coat of Borax.

I've had this happen on fatty fox as well. They sweat like a coon. Once the head is fairly dry I still flip them. They take a bit longer to dry.
But I would remove the heat, just use fans.

Was there fat left under the saddle after you fleshed it?

Very little if any

Should have took the saddle off. Now I'm in trouble!

I have never seen this before. I hand flesh them with a caribou from tail to nose, there has to be fat left on, or the saddle for this to happen.

Spruce