If you are going to be in the Florida Keys in May for Tarpon, you are going to need a BUNCH of crabs (which they will have at Hawks Cay) and a few of these rigs ready to go. Here is the exact rig we were using.
March is an excellent month for fishing the Keys. The entire 150 mile chain of the Florida Keys offers the possibility for a Slam just about any month of the year if you are with the right guide. This being said, the fish can vary drastically in size from one season to another. March will give you the opportunity at very large tarpon, big bones and big permit. I believe that March is one of the best months of the year to target a Slam with really nice fish of each specie.
Flyfishing for permit is difficult not because the fish are terribly difficult to catch rather that our flies and techniques do not accurately represent what they want to eat. Permit look at a dead crab the same as they look at a fly. The profile is interesting but not really what they had in mind. Flies need to have action resembling the real crabs and until they do, it is my opinion that they will remain exceptionally difficult to catch on fly.