Which numbers? 35 is our default, 60 degrees is considered a high bank angle but I know from personal experience as a pilot that you can maintain level flight at 60 degree bank, although it is very difficult and takes training. 15-20 degrees are the bank angles I used all last summer.

I agree checks like this shouldn't be in manual control. Manual control shouldn't be having anything to do with this at all. I've demonstrated how this problem is easily solvable, but you didn't like that solution. If you'd like, I will resubmit my approach for fixed-wing navigation: it is tested, doesn't have the screwball math this one does, works on CC3D-- which many users have requested--, and doesn't depend on manual control for setting anything beyond the flight mode.