Mike read the book and you won't worry about farting let alone belching.
Bruce VanSant made the trip down through the islands many many times in more than one boat before writing his book. He has far more knowledge of the trip than anyone on this forum, in fact is probably the number one expert in the world. You can take his advice with a grain of salt, if you wish, but he'll be the first to tell you, you're a fool, if you don't follow his advice. Read the preface first which states that this book is not for people on a schedule or with limited time. I also might add that many women find it offensive and he is as arrogant as the book suggests but people I have talked to who have followed his advice have stated it is bang on.