I've only read OotSP and The Screwtape Letters other than Narnia, both eons ago--I choked on Perelandra, which I remember you saying I should give another shot.

I suspect the Lone Islands are Lust & Chastity, obviously not in the sexual but in the spiritual sense. I would buy Coriakin's island as Envy & Kindness. That leaves Gluttony & Temperance.

I wish he'd written more, too. Have you ever seen Shadowlands?