Hi Will. I bought the UltraStudio Express a couple of weeks back since the UltraStudio 3D is not listed on the website anymore. I've been using the Express for a sporting event to record HD Pro Res 422 files onto a Pegasus R4 every day. I record 8 continuous hrs of footage everyday and haven't had any problems with the unit getting hot. Don't know how much more heat the 3D would produce, hope this helps.
I have a US3D that has been in service for a year, IT did have to go back for a replacement for the HDMI input but that was not due to the heat. IT does get hot enough to cook an egg and that is partialy why using the aluminum chassis on that unit was a good Idea to help dissipate some of it.
I have had it in enclosed spaces and on a wire rack during uses and sometimes running for up to 16hrs straight without problems. Just be sure to bring along some oven mitts :)
There was a review that I saw a few months back comparing the US3D to the the IOxt and when measured with a laser thermometer the AJA unit actually runs hotter. But perceptibly the US3D feels hotter because of the aluminum enclosure.
"Think of everything in terms of building capacity."