My dyno runs were done with the bonnett up and a large industrial fan blowing so I don't think heat soak would've been an issue. The engine bay will always be hot whether you are moving or not which is why the standard intake has a proper sealed box, not just an exposed cone filter.
I had a long chat with the Paul at RS tuning about this at the time and he reckoned that pretty much all after market filters were less efficient that the standard air intakes.
Even with the bonnet up your still going to get heatsoak, there's is no way even with a large industrial fan blowing that your gonna get enough air to imitate the natural airflow when driving at around 60mph, it's the air volume and velocity that matters not only the air velocity. Surely these companys cannot sell something that doesn't do what is stated, that means it was misrepresented in it's sale and everyone should be given refunds.