I know the keys pretty well.
can you better clarify your plans? what time of year, where are you going to launch, keep the truck/trl, anchor out, or marina's?
do you have current charts? and when you say come back the other side, did you mean going outside to the west, aound the barrier islands? (comming in at either big pine, or marathon).
pls clarify, and I'll try to help.
fyi: linky to noaa charts and google satilite mashup... (slow but good)
http://cruisersnet.net/south-florida-map/