Do not ever let someone tell you algorithms are easy and or fun... because neither is even remotely true, at least as far as the leap frog algorithm. It is the worst components of math and physics morphed into one giant equation of doom. I have figured it out, but only after 2 days of reading and failed calculations. I started and completed the graph and the functions needed to calculate the drag factor all I need now is the data from Halle and the true work can begin!!!