Heretic of The Seventh Circle
In the OP I used Indonesia as the largest island. Most are smaller, though there is probably a chain somewhere of “huge” mountainous islands that have a mountain rain shadow and look a bit like a drowned California Central Valley.@doctorbadwolf what is the largest island you are considering? England, Ireland, Honshu (Japan), Taiwan, Sumatra, Borneo, Madagascar - these are all pretty large islands, wherein most of the time, you don't actually feel like you are on an island. Comparitively, Shikoku, Guam, Hong Kong are small enough that you can walk their perimeter in a week or less, in some cases a day. Have you considered an upper bound on island size? (Heck, some may say that Australia or Antarctica are "islands", since they are not connected to another landmass).