I think you greatly overestimate the value of the large intercooler as a passive heatsink. I honestly think your setup is very dangerous because you have one turbo's portion of the intercooler almost completely blocked from any meaningful airflow. If i was designing a large core stock fascia setup i at least would have used the vertical style, so that each bank had some actively cooled portion of the intercooler.
oh well.. i suppose we shall see, but i am very sure that your idea of a big intercooler cooling just by bignesssake will not work out too well.