I have 4 identical fins that I can control independantly They are connected directly to 4 servos so I can control them "instantly" They are conected to 4 sides of a 10" octagon tube. As the ballon raises at 1Kft/min I am getting enough airflow over the fins to control it pretty good. My data above 30K ft is not so good because of "other" system issues. This will be fixed on the next launch. Near Space Balloon, Phoenix AZ Successes and Failures - YouTube
The "am I spinning" comes from either a gyro which seems to sensitive(I need to filter this better, make a quick iir filter with 5-10 taps). I am also looking at the last 5-10 compass readings, doing a liniear curve fit and finding the slope of the line (finding the derivative of the readings). Since I am reading the compass 5-10 times a second, the delay isn't to bad.
Hope this helps. I just need to try all of these new updates and then see what I need to do next.
Ken