You should write out a full alternate fingering chart. Go to the site I mentioned in an earlier post, write out the open harmonic series, including what's out of tune, and then write out the notes pressing your valves down will create from those open notes. Different horns might differ slightly from that model. Above G you can't play any note with any finger. Not in tune anyway. Double C can be played with 0 2 1 12 23 because of that small section of notes way up there that IS actually chromatic. (C C# D Eb E). Using those same harmonics you could play chromatically up from high G using 1&3, but then that would be out of tune anyway just like low D is.