I could have been off on my estimate.
Drove home from Elitch's (local amusement park) with the air temp in the mid to upper 80s. AC on and highway speeds. I watched the trans temp climb to just over 200. I installed the Hayden cooler shortly after using the method you suggested Mediamonkey- just unscrew the factory hardlines, push the fittings down and put the rubber hose on over. The hose supplied with the Hayden kit didn't want to go over the hardline flare, but with enough finese, brute and cussing it goes on. I secured the cooler via some aluminum strap and various fasteners from my collection. I didn't take pics because I did it all without removing the grill or bumper- just the top shroud that closes out the radiator. Sort of felt like I was assembling a ship in a bottle, but I got it done.
Also reconnected the rubber mat that sits behind the bumper and "scoops" the air toward the radiator- it had been just hanging straight down.
And painted the front skid plate with some bedliner just cuz.
Pressure washed the AC condenser and radiator fins really well. With that top shroud off I could see some gunk built up between them. Lots of black stuff ran down the driveway. Must have cleaned something off.
Went to the store as my test drive and took the long way round. The trans temp never got above 169. But I was driving with the window down. I've had the AC on every other time the trans temp has been high. Tomorrow I'm headed up into the mountains so that will be a good test for it.