Dual Transmission coolers

They were running a special online and I got two for the price of one with the thought of giving one to my brother in law. When I got them, they looked small so I installed both. 20 minute job (I'd recommend it). My question is, can two hurt it? I 'm thinking more too much restriction on the pump rather than too much cooling inthe winter time.

Here is cooler description:
Fluidyne Heavy Duty Low Pressure Drop/High Flow 11,000 BTU (10,000 BTU to 15,000 BTU depending on air velocity), 17,500 lbs GVW Rating Automatic Transmission Cooler is 1" thick. Oil Cooler Measures 14" X 6 1/2"

I am going to guess that you will be fine.
When the fluid is warmer.....it flows easier.
I would also verify that your radiator fans are running when your A/C is ON and your vehicle is sitting still (like in the driveway).
If the fans are not ON....and STAYING ON, your low speed dropping resistor could be defective.
Stop and go traffic is a time that your transmission is making a lot of heat....and having the radiator fans running will cool the transmission.
I turn my A/C ON in such conditions.......to cool the transmission fluid, and to keep the engine at a more consistant temperature.
The coolers don't do much without air flow.