Jerald, Thanks. You came so perfectly to the point of my quandry. You must have read my blog....Thanks for taking the time to look (there's more of the story posted there now).
Well, I'm still torn between 4x5 and 35mm....I guess I need to talk to the professor leading the trip to find out what to expect.
Do I understand correctly that one must stay with the "naturalist" guide while on the islands? If so, it seems that 35mm is the only option - as I doubt the Biology students will be too pleased to constantly wait for "the geek with the big camera".