ZF 6HP26 Coolant bypass

[mexicov]

Hi. New to AFF - bear with me. I have a 2010 FG XT, 6 speed auto. Warranty expires in two months. I travel a short distance (2 km) to work in freezing Canberra winters so transmission would not fully warm up. I am looking at using a PWR air/oil cooler to bypass the standard Ford transmission unit and avoid the "Milkshake" problem.
1. Has anyone had very cold weather (down to -8 deg) experience using the air/oil cooler? -over what time frame (years)?
2. If so, has there been any ill effects on the ZF 6HP26 transmission.
3. If I DIY, avoid any spillage, then totally fill the cooler and lines with the correct fluid, do I need to have a specialist go through the procedure for "topping up" the transmission? (Car has done 65000km and I was hoping to leave this until I have the transmission filter changed at 80000km).

Any advice would be appreciated. Thanks.
mexicov