Ok, I have been running my truck with the thermostat installed just like the OP has on his truck. My observations are as follows. Truck still takes a while to warm up. On my 23 mile drive to work it will finally warm up to about 130 in 15 miles. And usually has reached 150 by the time I am at work. This is with an outside temp of 40F. Once warm the trans shifts beautifully and the truck drives better and smoother. But, I also noticed that the truck is starting to shift better when cold. This has to be the result of the trans getting to the proper temp to go into learning mode. Thats the only explanation that makes sense. I do think that the best place for the thermostat would be between the radiator and the cooler so the fluid would get to operating temp faster but that is a much more difficult install from what I can tell. Might could be done easier with some fittings and extra hose so you could mount the thermostat in an easier spot. But overall I'm pleased and the truck is 100% better.
2016 Titan XD SV 4x4, Cummins Turbo Diesel,Magnetic Black. AFE dry high flow air filter, EZLynk w/Proven Diesel 60hp full delete tune, Pro4x wheels, polished tool box.