In my opinion, there's always been an issue with gravel runways in X-Plane. I tested the flight model on hard surface runways for it's takeoff and landing roll. Going on gravel, things went very bad. I haven't ever landed an aircraft on a gravel runway when I was flying, so I cannot tell how loose they can be. In any case, the Saab isn't meant to land on a gravel runway..probably because of the weight. The reverse thrust ratio of the Saab engines is only 0.2 of max forward thrust. So it is not really that much to stop it on a gravel runway. Regarding your 2nd issue, not really sure why you are getting these figures. We tested the flight model at several different altitudes and several different configurations. I'll have a look at it and see if I can duplicate your figures and take it from there.