Bitters: If you are going to Turneffe you will want the amber colored legs on an amber body or olive colored legs on an olive body. You can do the glue heads or just buy the Tears of Keys blanks which will save you a lot of time.
We used ragheads and small merkins rather than Turneffe Crabs and they worked well.
FYI-for turneffe you will want 90% of your flies to be weedless. Especially on the coral flats. Be prepared to lose a lot of fish to the rocks.