Had the opportunity to go down to Conrad Heatsinks today and pick up a pair of these puppies. Gee, they are big. 350x150mm in size. They are the MF35-151.5 and are rated at 0.21 C per watt for 80 C rise and weigh in at 2.46 kg each. See the Aleph PCB for size comparison. The guy was very nice and gave a good price to pick up and pay on the spot. These will be definitely in contention for the F4 build.