Joshua - thank you for the detailed reply - notably, your comment on Sony not yet having the right lenses for such a trip is a major reason i haven't taken it yet (although i had the 90 macro for a while and loved it, i just don't do much macro and went the 85mm route instead). In my Nikon days i had their 400/2.8 but now i'd just rent such a beast (it will be nice when that is available along with a faster focusing Sony body).
Great work as always and thanks for taking the time to reply in detail, eric.