I have no Subaru-specific data on that. Would be interesting to hear how common it is though.

I haven't changed my wife's stock radiator/ATF cooler setup in panic over the potential issue - which is either a considered risk assessment or laziness on my part

I think i might play it safe and go with the Golpher and the AFT cooler.
Im hoping for a replacement set and forget solution so dont want to have to be monitoring the temps and have to upgrade the AFT cooler later on down the track.
Considering it came from the factory with the lower tank in the radiator it cant be the worst solution (understand still not perfect though)

Good pickup on the Skid Factory Yowie, i was going to watch that on my trip home anyway - too hard to see what size it would have been as they have quite a few different models but it did look bigger than the one that i have.

Now to get my hands on a Gopher and list the Mishimoto for sale (brand new, fitted but hasnt had a drop of coolant)