Read the version I posted for hole 16 as version 4. I don't think you want to force players to land on the green from that distance for a long tee, ever. Have a layup area option similar to Winthrop 17 that doesn't allow a tee shot to land safe any closer to the pin than maybe 60 feet or so if they don't go for the island. You get a much better scoring spread with a version where players can get more 3s than any other score rather than mostly 2s & 4s which is a problem with pure "island only is safe" designs.
Another way to do it would be to use the buncr rule (no OB penalty) where the player has to throw twice from the long tee to land on the island then advance to the shorter tee and continue from there using buncr rule.
Rater of the tossed arc.