Why not just leave it open? The islanders will need that gate to keep out the giant snakes.
They should have built a man sized door into the big ones for easy access. Whichever engineer from the islanders designed it needs to be reprimanded.
The door had to be big. Kongs ancestors built the door for themselves.
Or why even bother with the huge door? Why not just have a solid wall, and a 10 foot door on the bottom that you can carry the sacrifice out, then quickly get back in.
Why not move? They had canoes.