Yes, you're right. Its named C3
The layout is similar to the U3. The mainreason for me to choose the C3 was the possibility of a cablemanagement behind the Mainboard. But for that, i had to cut some notches in the backshield.
In a U3 the mainboard is fixed directly on the outershield. So the cables cant be hidden and that causes a bad airflow.
Until yet i had no thermal problems, but I will bench it and tell you my results.