THM350 Questions

[PbFut]

I have never owned a THM350 and it is clear the present set up I am using is not correct. I am seeing temp at the exit of the cooler line close to the tranny reaching 250 degrees on very hot days. This in turn places stress on the coolant cooling system because of the in radiator tranny cooler. I am suspecting the tranny fluid I selected was a mistake. The newer tranny I had in Trail Blazer SS I own had to use Dextron 6 or it would really act up while towing. Thinking that would be a good fluid to use, I changed the fluid in my THM350 to Valvoline VI. I think the friction modifiers in the fluid is allowing too much slip and generating excess heat. My plan is to drain the THM350 and replace with ATI super F 30w. I know that is a ford fluid but read that it provides excellent results in a THM350. Anyone running this fluid?

My other question is fluid change. To get some of the fluid out of the converter, it is suggested to run the engine with the cooler line un hooKED to pump the fluid in the converter out. Then refilling with fresh. Assuming you don't run too long is this an advisable method for fluid swap?