Just like Sue, my VX was overheating on the Top of the World trail in Moab this year, and has done the same on hot days climbing long hills here at home too, so I've been trying to come up with a solution for this too. I've got 2 10 inch electric fans in my rig but they don't seem to be any better (or worse) than factory, besides not having to worry about my fan clutch exploding again.
An idea my dad brought up and something I have been thinking about recently is mounting a sprayer system to mist the radiator with water to help cool it a little extra. I believe the STi (Wormgod want to chime in?) has a factory setup for this to spray cool water on the TMIC to help with heatsoak issues.
At least one of the top drift racers in Forumla D has a setup like this on his car to keep from overheating between runs because they spend a lot of time just sitting on the grid waiting. Other teams just carry a sprayer like you would use for weed killer and spray it down that way between runs.