The McCoy's seem to not change rpm much from the beginning of the tank to the end on non uniflow where Foxes always leaned out quite a bit toward the end of the tank. And, the McCoy's seem to richen up on uniflow. I have run them both ways, and the McCoy's seem to run better on a standard tank set up. At least on the planes I have them on which are all profiles. Magicians, and Ringmasters. In a full fuse they may run better uniflow.