I'll probably get slammed for saying this but I am not convinced that heat soak is as big a problem in normal road driving as many people imply. I'm doing some data logging related to this at the moment but have not done enough to publish conclusive results yet. All I can say is that I've yet to experience any serious heat soak problems running in 30 deg C temperatures with a chipped AGU engine, a Forge SMIC and a vented wheel arch liner. Maybe if you're on serious boost for a considerable amount of time it will be an issue but with the kind of driving that I do, I'm not on the boost for all that long.
I've found that you do get a considerable build up of heat under the front wing if you've been using the car and then you have to stop or go slowly. It takes about 15-20 minutes with the car static for the under wing temperature to peak. However, if you get going again and stay off the boost the temperature does come down quickly. I've now fitted an extra vent at the top of the liner and, unlike the one directly behind the IC, you can feel the heat wafting out of that about 5 minutes after parking. Now in the process of doing experiments trying to fit a small fan in there at the top of the liner to vent that space. If this proves to be worthwhile, for me it will be more cost effective than a FMIC for normal road conditions.