When you transpose, practice with just the chords and a straight strum before adding the calypso strum. Don't try to do all of the transposing in one day. Do a different key each day.
ALSO - In preparation for playing the fun song SWAY, practice your Em and B7, moving back and forth between them. Remember to teach your fingers this shape without looking at them and without "building" chords.
This song plays consistently two measures B7, two measure Em, etc., through the whole thing except for 2 additional chords (briefly) in the Chorus so it is a great exercise for learning very well these two chords.