I don't know if it's THAT bad but you gotta input some reasonable worst case numbers. Size and throw angles are no big deal. Easy to measure and all. But the speed is the kicker. You need to figure out a reasonable terminal velocity for a longer dive and input that as a worst case. What that speed is depends a lot on the model, power source and prop. And in the end if this is a 3D type model with huge surfaces then you need to figure on YOU limiting the dive speed by not using full throttle or you'll require far larger servos.