We're going to take a weeklong sailing course and will be underway on the boat for 5 days. Looking for feedback preferably from someone who's done similar, but gladly appreciate feedback from folks who've chartered a boat and a skipper for a week. What is an acceptable amount to tip the instructor or skipper? Is it a percentage of the course fee (with or without books, certifications, tests?) per person, per couple, a straight dollar amount, etc.? 10% equates to $400-700/couple depending on the package/extras, but I don't know if the crew relies soley on tips or tips and commission from the company. I'm looking for the basic concensus and can adjust up or down depending on whether it was brilliant or below average. Thanks ahead of time.