I already have another thread running, about the airflow problem. I'm going to use 2 computer 12vdc fans, run directly from the 50V rail (with sufficient resistors of course). Oh, and those are old CPU heatsinks. The heatsinks are just where they are in the photo for demonstration purposes. They will later be mounted in the back of the box. Now it's up to me to try and make the holes for the fans. which will be quite hard, since I don't have a circle drill of that diameter.