What are appropriate gifts for a primary student's CFI upon certain milestones, such as a successful solo and a passed checkride? I was thinking champagne (something nice, but not like Dom or Krug) after solo and scotch (Walker Blue?) after checkride, but I don't have a sense of what the common practice is. If I've missed any major milestones where a gift is appropriate, please let me know - I don't want to be "that guy"! Thanks in advance.